I love how you ask us in the peanut gallery for our opinions. Having gone through the pain and experience of learning when and where to pick my fights, this sounds like a situation where letting go would be the best move.
It would be good karma.
In fact, you never did get bumped, so there was no event for which compensation was necessary. Moreover, the fact that you get treated like a king pretty much wherever you go w/in the United world is pretty cool too.
The supervisor probably offered compensation because he/she is so used to dealing with asshole business fliers whose egos require something more than a heartfelt apology. People screw up - front line people have sick children, they go through divorces, they have bad news.
Don't get me wrong, agents should not let this bleed into their work day, but we're human, and it happens.
Plus, you don't want to be one of those entitled people. I see them every day, and they have lost sight of reality.
My advice? When you see him next time at IAD, sincerely thank him for his heartfelt apology (I think that along was pretty cool what he did). Since your face is so well known, that might spark his memory. If you do this sincerely, Karma may very well reward you! 🙂