That's an amazing experience even if you couldn't recognize it at the time. That's legitimately cool, and you can say you were in the room with genuine once in a lifetime talent. Not everybody has that experience.

I saw Dave Matthews play a very small show (like 30 people were there maybe) when I was younger while we waited for change to make a phone call. I didn't really pay attention, but remember thinking that this guy was really weird and really different and really really good. I wish I had stayed for the entire thing and maybe talked to him. But, at least the memory is there.