When I was an Army Infantry Sergent in Germany in the 80’s, one flew 100+ feet over our position. It came up from behind us and flew directly over my track. Never heard a thing till is was already flying past us. Damn scary to know that you would have been dead and never even see it coming.
There’s a good chance that he didn’t see you either.
People over-estimate the ability to pick out a man-sized target from an aircraft moving that fast, even at that altitude.
Generally, if he can see you, you can see him.
And the A-10 is a bigger target.
Probably why the A-10 doesn’t fly in ADA-rich environments.