It is a trivial issue because the chances are pretty good that you will never actually encounter that situation, and if you do, there are alternative means of dealing with it, such as having an escort. Women always go to the bathroom in pairs anyway, if you hadn’t noticed - they’ve solved the problem long ago, and they do it precisely for that reason.
Good thing rapists know that women travel in pairs. That must be why we haven’t had any in the last 1000 years.