I've spent some time this week dipping into a book called "Missing Masterpieces", in which a man called Gert-Rudolf Flick presents case histories of 40 great works of art that have disappeared from the face of the earth. The book is not exactly what you would call a rattling good read - it's about as exciting as waiting for final election results - but the subject is fascinating.

Works of art do go missing all the time, for a variety of reasons. Fashions change, and people aren't as careful with things no longer considered as good (or worth as much) as once they were as they are with things still fashionable and, therefore, valued. In institutions, things are set aside and forgotten, or perhaps misidentified. In private homes, familiar things can acquire a kind of invisibility.

A painting recently discovered hanging on someone's landing, for example, was identified recently as a Cimabue (the name taken by a 13th Century Florentine painter originally called Cenni di Pepo). Cimabues are so rare that when the find was eventually sold at auction it was the first time that a Cimabue had gone under the hammer. The picture now hangs in the National Gallery in London.

Another painting, `The Seizing of Christ', hanging in a monastery in Ireland, had for years been catalogued by the monks as something by a 17th Century Dutch painter called Gerrit van Honthorst. It turned out to be a Caravaggio, long thought to have been lost.

Wars have an effect as well. We read every day about the shifting ownership of art stolen during the Second World War, but the English Civil War, the Thirty Years War, the Napoleonic Wars and the French Revolution are all also examples of conflicts that served to disperse big collections of art. War is also often the cause of the sudden disappearance of pieces of art ... the coalition invasion of Iraq is a perfect example of how that sometimes works. Some of the most extraordinary old masters have vanished from the face of the earth.

If you follow news in the arts world, you will have read about a controversy in Italy that has been going on for 11 years, now, about whether to use a dry method to clean Michelangelo's `David', or one in which distilled water is used. The argument has just been resolved, last week, in favour of the riskier wet method.

That `David' is part of the collection of Florence's Galleria dell'Accademia, and is one of the most familiar objects in art. There is also an earlier, smaller `David' by Donatello, in which David is carrying a long sword and wearing rather an odd hat, which is held by the Museo Nazionale del Bargello in Florence. And there is another by Andrea del Verrocchio (he taught Leonardo da Vinci), in which an androgynous David stands in skin-tight body armour and a little skirt (I'm sure there must be a manlier word for it, but I don't know what it is), dagger in hand, with the head of Goliath at his feet.

This is also at the Museo Nazionale in Florence. There are others - David was quite a common subject for artists in the tiny, powerful city-state of Florence, perhaps because they identified with his giant-killing propensities.

But there is ... was, probably ... yet another `David', also by Michelangelo, cast in bronze, that was so famous in its day that it was celebrated in an address at Michelangelo's funeral. It has been missing since the 18th Century - and was probably a victim of the French Revolution, in the sense that the connection between the statue and Michelangelo, its maker, had been lost, the last member of the French family that owned it was guillotined by the Revolutionaries, and his possessions confiscated or burned. In this piece, David is said to have a foot on Goliath's head, as if grinding it into the ground.

The big headlines are given to thefts, though. If we leave aside what has, or perhaps has not happened in Iraq recently, the most dramatic recent heist was in May, and involved a salt cellar worth $57 million (give or take) from the Art History Museum in Vienna. As you can imagine, it's a pretty special salt cellar. Saliera is a golden sculpture - an allegorical representation of Earth, depicting a bearded man with a trident, symbolising the sea, leaning back and resting upon the head of a horse. The man stares at a naked woman, symbolising the Earth, whose legs are intertwined with his. There's room for salt in a little richly decorated temple on the ground beside her.

Quite apart from having a considerable aesthetic value of its own, the Saliera is also the last remaining authenticated example of the work of the Florentine master Benvenuto Cellini.

According to the FBI, who keep quite a detailed website dealing with stolen art, thieves simply climbed some scaffolding on the outside of the Art History building, and were able to get in by breaking a window on the second floor. Lax security was a factor in this, as in many other incidents. The reality is that thieves don't really need to be shinning down ropes from skylights, dodging laser beams, ? la Topkapi, because few public institutions take that kind of expensive care of their collections.

A 31-year old French waiter called Stephane Breitwieser stole 239 art treasures said to be worth over a billion dollars in seven years, until November 2001, when he was caught, from smaller museums and galleries in France, Switzerland, Belgium, Holland, Denmark and Austria. His normal method of operation was to cut paintings out of their frames, roll `em up, stick `em under his coat and walk out. He stored his collection in his mother's apartment in France.

Tragically, it took Swiss police a week to get a warrant to search his mother's apartment. By the time they served it, the mother had taken a pair of scissors and cut every painting in her possession - works by Francois Boucher, Antoine Watteau and Peter Breughel, among many others - into small pieces. She threw them out with the trash in an attempt to get rid of the evidence against her son. She also threw over 100 pieces of jewellery, statuettes, bits of silverware and antique watches into a canal. Many, though not all, were recovered. The most valuable painting Breitwieser stole, and his mother destroyed, was a 16th Century painting by Lucas Cranach the Elder said to be worth between $7.5 and $10 million.

My idea of punishment for crimes like this one probably comes from a long-ago reading of a Boy's Own Book of Genghis Khan in China, or something like it. Sadly, the Khan's brand of justice never quite made it to Europe. A Swiss court sent Breitwieser to prison for four years - but with time off for this and that, he's likely to serve only a few months. The mother is being investigated by the French police ... but we know the rest of that story already, don't we?

When thieves targeted Edvard Munch's 19th Century masterpiece `The Scream', they managed to get in and out with it in under two minutes in broad daylight. Luckily, the police managed to recover that painting quickly - a recent BBC story about art theft said stolen works of art normally take between five and seven years to re-surface. Several major works of art by the likes of Rembrandt, Titian, Klimt, Matisse and Turner have not surfaced in that kind of period of time, giving rise to the theory that they might have been stolen-to-order for collectors. (The BBC story lets a little of its much-denied bias show in the lead paragraph, which reads in part, "Art theft is no longer just an elitist crime funded by unscrupulous collectors...".)

In June of this year, to give you an idea of the scale of art theft, Interpol released a CD-ROM database containing 17,000 photographs of stolen valuables. The organisations says it has about 14,000 major art works on its files that have been reported missing from museums, galleries and individuals around the world.

But I wanted, in this article, to relate to you a happy story, concerning the re-appearance of a superb little work by the Baroque painter Annibale Carracci, which dropped from sight about 300 years ago, and turned up this summer at Sotheby's offices in New Bond Street in London.

`The Montalto Madonna' is named after Cardinal Alessandro Peretti Montalto, who commissioned it some time around 1598. It was a work that was greatly admired in those days, and much-copied. It was last mentioned around 1672 as having been in the collection of Lorenzo Salviati, member of a prominent Roman family, related to the Medici. After that, nothing. When the little copper panel was taken in to Sotheby's, it was at first assumed that it was one of the many copies of the original. The quality of the painting, however, spurred the staff of the Old Master Painting department to do a little further research. Starting with an 18th Century inventory number on the back of the canvas, they began a painstaking process of reconstructing the painting's provenance. They discovered that the number matched that given in an inventory of the possessions of the Colonna family in Rome.

Looking at contemporary accounts and other inventories, Sotheby's traced the ownership of the painting back through various generations of the Colonna family, through earlier generations of the Salviati family, to Cardinal Montalto, who commissioned it. After the date of the Colonna family inventory, though, ownership was harder to trace. It was the frame that gave the vital clue, in the sense that it had been made in the 19th Century, and it prompted Sotheby's to look back through records of contemporary English collections.

Sure enough, the Madonna was mentioned as being in the collection of Sir Archibald Campbell of Glasgow. He acquired the painting while travelling in Italy in the 1820s. His inventory number was confirmed as being that on a corner of the frame of the picture that had been handed over to Sotheby's, establishing a vital connection between Sir Archibald and the Colonna family.

When the Scotsman's house in Glasgow was sold on his death some years after he bought the painting, his possessions were auctioned off. The painting was acquired by Glasgow University and correctly ascribed to the painter Carracci, but not recognised as the Montalto Madonna.

Once the provenance of the painting was established, stretching all the way back through 300 years, it was sold in the same Sotheby's auction in which a recently-discovered Rembrandt self-portrait fetched $11.3 million. The Madonna was sold for $1.3 million to a London dealer acting for the Italian city of Bologna, which was the city in which Annibale Carracci was born and grew up. So, you read it here first - a pleasant story with a happy ending. Who said the press always concentrates on the bad news?