Actually, I usually say "he/him" when I think "indeterminate gender" since the gender-neutral masculine form is well-established in English, eg, "actor" may refer specifically to males in contrast to "actress" but is also the accepted gender-neutral form. While the singular "they/them" goes back a long way, it was never very popular until the feminazis recently overpowered the grammar Nazis for pronoun supremacy. I'm somewhat old-fashioned, so I've always sided with the grammar Nazis is this battle, but I'll still admit that singular "they" is better than "he/she" or worse "(s)he", which is really just a cop-out for indecisive writers who don't want to pick sides.

It's not their job to help you pick an appropriate pronoun. If you need help, Fowler's Dictionary has an excellent enumeration of the pros and cons of each, in the entry for "they, them, their".

The mere fact that someone is female does not give you permission to make unwanted sexual advances towards her.