The preponderance of comments that "this has happened to me and I'm a guy so the world's not sexist" is so discouraging. It's logically inconsistent and a giant sign of a defense mechanism.
It's a problem and you might do some of these things inadvertently, so maybe listen a bit more and figure out how to keep yourself from not doing things like assuming women at a tech conference are in marketing instead of engineering.
The fact this thread is filled with a bunch of guys mansplaining how this wasn't sexist behavior is very telling.