Once again I'm on the hunt for a book (short story?) I read several decades ago. It's not the children's book. Have you ever put something down--a pen; a watch; a calculator--come back a few minutes later and can't find it, even though you're sure that's where you left it? Of course you have--we all have. Then after giving up you go back there a short while later and find it's just where you left it! The book I'm trying to find--or at least a short fiction story within a book--explains all that quite cleverly. There is a civilization in another universe that uses a space-warp to reach through, take items and reproduce them for their own use without the need for costly technological research. Ideas anybody?