I am be dense or its late at night. Were you en drab in the ladies' room when the woman confronted you? If that is the case that is different than en femme using the ladies' room. Are you certain or you just assumed she identified your voice as belonging to a man attired as a woman?
In my city, all single occupancy restrooms must be identified with male and female signage. That was instituted at the request of the transgender community.
