We'll reshelve it for you. Teach your children to respect the books in the store. They need to understand that these are products for sale, and if they tear a book, you should offer to buy it. Pick up after your children and insist that they help you. Do not let your children climb the bookshelves or otherwise consider the store a playground.
Books are heavy and have pointed corners so they can be quite painful when they fall.
At least do not put drinks down on top of books. The store can't sell sticky or wet books. Do not berate the clerks for not having the book you want. We aren't the buyers. If the computer says the book is in stock, and it isn't where it is supposed to be, then the book has been recently purchased or someone has not put it back in its place.