One possibility is that the screens are only hidden. See the information in Organize the Home Screen and App Library on your iPhone - Apple Support including the following:
With iOS 14 and later, you can hide pages to streamline how your Home Screen looks and add them back whenever you want. Here's how to hide a page:
- Touch and hold an empty area on your Home Screen.
- Tap the dots near the bottom of your screen.
- Tap the circle under the page that you want to hide.
- Tap Done.
To unhide a page, repeat the steps above. Then use the App Library to quickly find apps hidden on different pages.