Have you tried contacting Meir Yedid personally? You can contact him at email@example.com
Some of the books may still be available. Since he produced 5 editions of the W.O.W. book test, each of which involved 2 different hardcover books, there were a total of 10 books in all. Do you know which one you are missing? As I have 4 of the 5 editions in my collection, if you don't recall the title of the one you lost, but can provide the title of the one you still have, I can probably determine the title of the one you're missing. (Unfortunately, none of mine are for sale, but at least I may be able to help you identify the one you're looking for.