This may have already been asked, but is there a way to search to see if someone is looking for a book you may have?

you can tell if a book you have is WL by putting the ISBN # into the search up at the right.  Or logging them into your TBR. 

If it's on your bookshelf then your version of the book isn't WL.  you can look to see if there are other versions that are WL. But unless the bindings are very similar and there aren't many copies of yours posted-then I would assume they really want that WL versions-especially if it's audio or large print-or yours is a paperback with lots of copies posted and the WL is for hardcover.  you can tell how many copies of a book are in the system by putting it on your reminder list.