I mean seriously, if I can't get a Miss or a Madam dressed this way
who can??

(kidding)

It was while I was buying lunch from a salad bar, the woman hands back my change and said "thank you, sir". I was a bit stunned, it took me a few seconds to put my brain into gear, but then I asked her "did you just call me 'sir'?" She apologised and said she had done it by accident, I just kept looking at her with an "are you serious?" look - she squirmed a bit more and she apologised a few more times. I shook my head and walked away.
I guess I should have a better sense of humour about this sort of thing and be should have been more gracious and accepted her apology but it really made me feel lousy and angry. I actually felt I looked pretty decent and getting called "sir", accidental or otherwise, was a massive kick in the guts.
Oh well, tomorrow's another day... I'm not going to let it get to me, just needed to vent.