you probably 'removed' it..
to locate it again:
From your Home Screen, swipe left until you get to the App Library.
Swipe downward and you'll get an alphabetical list of your apps.
Locate the app in the list or type the app name into the search field
Once you've located the app, tap/hold until it raises/selects, then drag it and it'll pop out to your Home Screen
Organize the Home Screen and App Library on your iPhone - Apple Support
for issues deleting:
review this
How to delete apps on your iPhone, iPad, and iPod touch - Apple Support
you can delete from the App Library by locating the app and tap/hold, select Delete App
or you can go to Settings > General > iPhone Storage > [app name] > Delete
If you still are unable to delete, check:
Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Deleting Apps
make sure that's set to 'Allow'