This reminds me of the Ren & Stimpy episode where they enter a black hole and finds all the missing left socks in the world:
I don't think I've ever lost anything important, but there are several cds and movies that I out of the blue can't find. I probably borrowed them to somebody, and they forgot to give them back.
I think it all works out in the end though, because I also have several cds and movies I can't remember buying, and I can't remember who I borrowed them from.