I spend a lot of time wandering around the house looking for whatever book I happen to be reading, but I am almost always successful (fallen behind radiators is a good bet. Or the top of the toaster, that being one of the few surfaces in the kitchen that is always free of clutter. Except when it has a book on top of it).
But that is not the sort of lost book I have in mind at the moment--I'm thinking of those books read once long ago, that your parents left behind when you moved and you have never seen again. Here is a most excellent website that organizes all the places you might go on line to find those books, and I can't think of anything to add to it.
But if anyone ever read a book about a boy with (I think) a club foot (or perhaps some other issue related to walking), who lives on an island and bird watches (with some sort of bird related triumphant conclusion), that ends with the boy riding the bus to the school on the mainland, please let me know. It could be an English book, because it was left behind in the Bahamas when I was eleven, along with all my Enid Blytons (not that I hold a grudge). Whereas for some reason all the hardback Nancy Drews were lovingly packed, and I have no desire to ever read them again, and this summer my mother wants them out of her attic. I vote we sell them, but then wonder if someday I will have a granddaughter who will spend a fortune buying them all over again....Fortunately I have been able to replace the majority of the Enid Blytons at a reasonable cost.