iPhone sending ghost notifications

The other day I got a notification on my iPhone, but when I went to look at what it was, there was nothing there. I just assumed it was someone else’s phone. Then it happened again on my desk, but there was no notification. Again, I assumed it must have been someone else’s phone. Today I was by myself with my AirPods in and I heard the notification sound but there is no notification. I’m happy I’m not going crazy, but does anyone know how to fix this?

Possibly you've set one of your apps to make sounds, but now show notifications.

To check this, scan your Notifications settings for an app that only has "Sounds" on.