When you are in the search area, it shows the tab where the item is located in the Creative Inventory. When you sign a book, it shows the tab as "craftingScreen.tab.none", Instead of "Items". (Sorry about the picture I don't have a very good webcam. I would take a sreenshot but I use Xbox so I have to use this laptop's built-in webcam.) (Also I haven't used books in a long time, so there might be other versions that this bug effects.)