I can’t seem to find my Settings app. Suddenly it’s disappeared

Try a spotlight search.

Swipe down from the middle of the home screen to get to the search. Type in Settings in the text field at the top. The Settings app will appear in the search and if it is in a folder, the name of the folder will appear to the right of the app name.

Since you CAN NOT delete the "settings" app, that icon could have been accidentally moved to a different screen page or "hidden" into a folder. Check better.

Regards

Giulio