The App Library holds all your apps always. Wether they can be seen on the Home page or not, they are always in the App Library. It's juts a complete listing of all Apps. You can choose to not use it however if you don't want to.
As to your home page disappearing, try pressing and holding on an app until they all shake. Then tap on the line of dots at the bottom of the screen to bring up the Home Page manager. Make sure your home pages are checked to be visible. Press Done when you have checked all pages. They should all be back and accessible.
Link-> iPad User Guide - Apple Support