Having worked in the same place for four years, this happens to me constantly. I know my coworkers don't do it on purpose. Most of them have known me as my birthname for at least two years, at least half of them the whole time I've been there. It's just really frustrating when someone will be like "oh, round boy with the blond hair and glasses was helping me and told me (x)." And they'd be like, "Oh, that's (birthname), SHE's a girl." It happened a lot right after I started binding (and, to be fair, I wasn't out then), but after I came out, they were doing it a lot less.
But this one time, right after The Dark Knight Rises came out on DVD (so we're talking Fall 2012, before I was out to almost anybody), this guy asked me a million times if TDKR was the new Batman movie. I told him yes at least five times before he stopped asking. I may have been slightly annoyed. So anyway, I come back around and the guy says to me, "Hey, you got something to say to me?"
"No, sir, I don't." I'm confused as all get out.
"You were really rude to me. I didn't like that tone you got."
"Sir, I thought you couldn't hear me, as I'd answered your question several times."
He's in a mart cart (one of the motorized ones) and starts down the aisle. "Little ->-bleeped-<-head. If you were a REAL man, you'd come outside and fight me and I'd kick your ass."
"Sir, I don't appreciate being threatened." One of the guys I work with is on the walkie trying to get management out on the floor at this point.
The guy rolls up to me in the mart cart, stands up (towering maybe two inches above me and being in no way threatening), and says, "Well, I felt threatened when you made me feel stupid." and he gets back in the cart and rolls away.
I wasn't binding at that point, just wearing compression shirts. And one of my coworkers says, "But you're a GIRL."
THANK YOU FOR RUINING MY BADASS MOMENT. Ugh.