"WHAT!!" he bursted out

The idea that you really didn't know who he was, was really suprising and kinda disappointing to him, he'll admit it. Especially since he's in such a popular band. It made him feel a bit less loved and well-known than he originally thought- and that slightly hurt his ego, if he's being completely honest.

"Seriously! I'm legitimately Adam! The world's famous rockstar? How in the world do you not know anything about me??"