Happened once -- hair not that long, but down, wintertime, wearing an overcoat (which I guess could be considered androgynous?), at the supermarket. The bagger asked "Paper or plastic, ma'am?" I heard "man", not "ma'am" -- I wasn't even trying. So I said "whichever, it doesn't matter," in a less than completely feminine voice (not trying, see)...
He was so embarassed and apologetic.
Oh, I just melted!