If you can't find it at home, wait until you get to school, look in your desk, and then ask your classmates if they have seen your book (last time I couldn't find my physics book because I left it on my classmate's desk, so neither of us could find it, and he put my book in his pile). No one will get your book because everyone has a book.

If you really can't find it, go to the bookstore and buy a new one.