I have not found a way to locate the placement of an app in my many pages of folders on my iPhone home screen, short of looking through every single folder on every single page.
Before you say "use the search feature" let me point out "search" does not actually allow you to find anything—or, if it does, it's very hard to figure out how. The so-called search feature gives you an alternate launcher, but if it can be used to tell you where your app icon is in the many pages of your home screen, buried in the many folders on each page, I have not figured out how to make it do that. If all you want to do is launch the app, then "search" is okay. But if you want to move it to a certain folder, then (as far as I can tell) you're out of luck.
At least as of March 2020, when I'm writing this. Apple has finally given us the ability to delete things from the App Store, so they're on the right track. But I am failing to find a way to find things. Is there a way to do it?
Update:
See my answer below to connect the dots between the problem and jmh's solution.
Best Answer
If you have Open_Term or another app that you can use the command line on, go to that app and cd into your directory. Then type ls -laRt. That will list all the contents of all the folders. You can then search the output for the app you want.
It's a lot to do for what you want. There should be an easy and automatic way to do this.
You can also use the spotlight search which should give you the folder the app is in. From your home screen slide the desktop to the right to get the window where the widgets are are accessible. At the top of that window is a search bar. This is the spotlight search. Type the complete name of the app in the search box and hit return. If there is only one match it will list the folder where the app is stored.