How to find or reinstall missing apps on iPad
Facebook and email apps have disappeared
How to find or reinstall?
[Re-Titled by Moderator]
iPad Air 2, iPadOS 15
If Spotlight Search isn't offering an expected App, you'll be able to find all Apps already installed on your iPad and iPhone using the App Library. If Apps have been offloaded or uninstalled, they can be reinstalled from the Apple App Store.
To access the App Library page, simply swipe to the left from your Home Screens; the last page is the App Library. Here you will find both automatically curated App groups, an alphabetical list of installed Apps - and a Search tool.
After opening/using an App, it should be visible in Spotlight Search - unless they have been excluded in your device settings.
More information about using the App Library can be found in the respective User Guides:
Find your apps in App Library on iPad - Apple Support
Find your apps in App Library on iPhone - Apple Support
Additional information for Spotlight Search can also be found in the User Guide: