app on iphone

With iOS 14, apps can be removed from the home screen without being deleted. If you have iOS 14, go to the App Library (swipe left past your last home screen). From there you can touch and hold an app and slide it left back to the home screen.

Or if it was deleted, see the following from Delete built-in Apple apps from the Home screen on your iOS 14 or iPadOS device or Apple Watch - Apple Support

Restore a built-in app that you deleted

1. On your iOS or iPadOS device, go to the App Store.
2. Search for the app. Make sure that you use the exact name of the app. Find the correct name of built-in apps.
3. Tap  to restore the app.
4. Wait for the app to restore, then open it from your Home screen.

If the App Store only gives the option to Open the app, that means that the app is already installed on your phone.

Try using Search to find it. Swipe down on the home screen, starting the swipe down from the middle of the screen. See: Use Search on your iPhone, iPad, or iPod touch - Apple Support

Also see the following from my previous reply:

With iOS 14, apps can be removed from the home screen without being deleted. If you have iOS 14, go to the App Library (swipe left past your last home screen). From there you can touch and hold an app and slide it left back to the home screen.