A. It's true. The Pigeon hates it when I make books that aren't about him. So, he hides in every book I've ever illustrated. He's easy to spot in DON'T LET THE PIGEON DRIVE THE BUS!, but harder to spot in some of my other ones.
If you can't find The Pigeon, you probably haven't looked hard enough (some of them are tricky!).
It could also be that you're reading a specially bound book for schools or libraries. Sometimes the binders or librarians remove pages or put stickers over the hidden Pigeon. Even The Pigeon can't do anything about that!