Steps to reproduce the problem:
1. Open Chrome and go to the demo https://airhorner.com
2. Go to the 3 vertical dot menu to "Add to Home screen". (It is assumed you have never added the app to the home screen before.)
3. Press "ADD" when the "Add to Home screen" dialog pops up.
4. Close the browser.
5. Observe the Airhorner app on your home screen. So far, so good.
6. On the home screen, attempt to uninstall the Airhorner app you just added. That means you may long-press to pop up the "Uninstall this app?" dialog. Press "UNINSTALL".
7. Observe the Airhorner app has disappeared from the home screen.
8. Repeat the steps 1-4
9. The Airhorner app will NOT re-appear on your home screen. That is wrong.
10. Go to the "Settings" -> "General" -> "Apps" 
11. Uninstall the Airhorner there.
12. Repeat the steps 1-4
13. Now, observe the Airhorner app on your home screen again.

In short, the uninstall on the home screen misleads users. The uninstall there does not really uninstall the app. The "Add to Home screen" misleads users further if the hidden app is not uninstalled by the "Settings".

What is the expected behavior?
After uninstalling an app from the home screen and adding the app to the home screen again, the user should see the app on the home screen.

What went wrong?
After uninstalling an app from the home screen and adding the app to the home screen again, the user will not see the app on the home screen. 

The user has to go to the "Settings" to uninstall the app in order to re-add the app to the home screen.

Did this work before? No 

Chrome version: 66.0.3359.158  Channel: stable
OS Version: 6.0.1
Flash Version: 

The "Add to Home screen" becomes a critical feature by now because your recent (M66) <audio> autoplay policy change requires that. Without a reliable "Add to Home screen", a lot of apps with autoplay will not function at all.