He definitely thought I was an idiot

I'm sure people respond that way all the time. He probably didn't even notice.

"Oh hi! How you doing?
"Good. How are you?"
"I'm good. How bout you?"

"Here's your ticket, enjoy the movie"
"You too!"

I work in food service and this happens all the time:
"Alright, enjoy your meal!"
"Thanks, you too."

"I sell hair, and hair accessories."