Use Flightradar24 next time. The app has an “augmented reality” function that will identify the aircraft when you’re pointing your camera at it.

Then you’ll at last know if it’s 2) or 3). And if it’s 2, you’ll see if it’s a) or b).

If you’re in the US, and the flight you’re seeing is a potential 2b), go to https://www.thinkaviation.net/restricted-airspace/ to see if there’s any active restricted airspace in your area..

If the aircraft is potential GOV without a transponder, and outside an active restricted airspace, you might be up to something.

Good luck with your digging.