This happened to me a bunch of times. I didn’t get upset because I don’t think it’s insulting to be taken for a service worker. Service workers aren’t inferior to professors or physicians.
The last time it happened was at Macy’s, and it was an older black woman who thought I was the store assistant. I said, “I’m sorry, I don’t work here. I think the assistant is over there, let’s go ask her.” Then we had a nice little chat about what we were shopping for.
It’s sad to see physicians in such a tenuous psychological state.