Maybe it's in the App Library. Check the App Library first.

Find and open an app in App Library.
1. Go to the Home Screen, then swipe left past all your Home Screen pages to get to App Library.
2. Tap the search field at the top of the screen, then enter the name of the app you’re looking for. Or scroll up and down to browse the alphabetical list.
3. To open an app, tap it.

If a category has a few small app icons, you can tap them to expand the category and see all the apps in it.

App Library on iPhone showing the apps organized by category (Photo & Video, Social, and so on).