How to restore an app to a Firebase project If you need to restore an app that's been removed from a Firebase project, you can do so within 30 days of the app's removal.

1. Sign into the Firebase console, and then open your project.
2. Click the Settings icon, and then select Project settings.
3. In the Your apps card, click Apps pending deletion.
4. In the row for the app that you want to restore, click RESTORE APP.
5. Confirm the changes that will occur with the restoration of the app.
6. Click Restore app.

For reference please go to How To restore your deleted Firebase Project