I’m open minded, but for someone to travel half way across the universe then not to say hi would be odd, well from a human point of view.
As for states using such vehicles I could totally believe it, didn’t the US do some experiments to see if their “UFO’s would be reported and how.
Incidentally I watched something on Sky last night about the bug in a US embassy for 7 years! and it was fascinating, see
https://hackaday.com/2015/12/08/theremins-bug/