When I bought a 280z from a guy in the US he mentioned that he may have a few more. He recalls parking them up at his mum's house but would need some time to find them. He did get back to me a week or so latter and said he had manged to find 3 more and sent pictures of them in different barns. I did buy another one and wished I had bought more. He had quit a few but he mum's land was so vast it took a very long while to get to all the possible places. Hard to comprehend really but if your estate is the size of a typical UK county then I guess cars get lost.
I did get chatting to a guy at a an Eric Euipe car club I'm a member of. He was an old guy who kind of resembled a tramp. When I asked which cars he liked, his reply was all sorts. He liked aston's and had a few. Also Jag's which he has lots of. mainly old XK's. He had a phase of collecting famous rally cars. He own Peter Seller's old mini along with a few other famous cars. When I asked where he kept them all he said lockup garages all over London. He admitted to have lost track of many but every now and then he rembers where he put one and goes to see if its still there. These people are among us.