You might have moved it by accident into a folder of icons.
You can look for it in Spotlight, swipe down on the icons, type the name of the app in the search text box, it will show the app and the folder within which it resides.
For example, see how I find which folder holds Pro HDR X app, below.
Swipe through your screens or try a search.
From any Home screen page of your iPhone or iPad, touch your finger to the screen and drag down to reveal the Spotlight search field.
2. Type what you're looking for and hit Search.
iPhone app installed but no icon
