There was a story about a priceless violin.

I heard this story 10 years ago. A famous school (I think it's UCLA) used to own a Stradivarius violin (could worth over several million dollars these days). They loaned it to a violinist. One day that guy left the violin on top of the car one day at a gas station, and he drove off. Someone else found it. Not knowing it was a Strad, he kept it for some years and then passed it to his nephew. The nephew was going to sell it and that's when they realized which violin it was. UCLA of course wanted it back, but, finders keepers. Eventually the nephew lets the school use it on borrowed terms, but keeps the ownership.