"Thank you for your service"

I'm currently TDY and I was taking the hotel elevator. A lady sees I'm in OCPs and she says "thank you for your service". I autistically replied, "ahh, well thank you for paying your taxes".

Normally I get a chuckle but this lady stayed silent and stared at the elevator door. It seemed like time stopped and the cringe/awkwardness was overwhelmingly palpable. After what must have been a few seconds, I could see through my peripheral vision that she was turning as if to say something but she changed her mind. The silent elevator ride down with her was worse and I wanted to crawl out of my skin.

What are you supposed to say when people say TYFYS? You're welcome?

Little bacon cheese burger no mayo and a small vanilla milk shake.