Yes. Even if you don’t know the reg number, if you know the airline, you can look up the fleet, find the airplane at Tehran, check the flight. If it doesn’t show the airplane moving on the map anymore or the speed/altitude, and the last transmission is at 8.000 ft/275 mph, houston, there could be a problem.
No, I was thinking of DIFFERENT flights from the one that crashed. Flights that left shortly before the doomed flight and shortly after. The possibility always exists of MISTAKEN IDENTITY if something nefarious happened.