Considering their rarity and value, Stradivarius violins seem to be the most carelessly handled items in the world. There are about 600 of them and in the last three years, one was left in a cab, and two on trains (the latest story of lost and found is here ). The stories follow a pattern-someone who has borrowed a Stradivarius from the real owner carelessly leaves it and it is found by a good Samaritan who turns it in to the Lost and Found. Given the loss rate of Stradivari, it appears that people take better care of their Ipads than they do their $20 million violins.
I have a bit of experience in tracing and finding higher end stamps that go missing and here is what I think is really happening. The violins aren’t lost; they are stolen. But stolen by amateurs who quickly realize that the violins are impossible to sell and who, not wanting to destroy them, arrange for them to be dropped off at the Lost and Found in exchange for no questions being asked. Very high end works of art are very difficult to sell as they can never be shown (or played) and the buyers never have good title. In stamps the low theft rate of philatelic material is evidenced by the extremely low insurance rate that collectors and dealers pay (the rates for smaller collections are little more than the cost of actually writing the policies themselves). And the Internet has made theft of rare property even scarcer. Scanning provides a permanent record that allows collectors to identify even less valuable stamps.