You have no idea if he's got a dick.
You just saw a big bearded dude follow your daughter into the restroom.
What's the next step? Let him go and assume he has a vagina? Ask him to show you?
You're right, I don't. And yes, if it followed her in, I would be concerned.
What would I do about it? Probably nothing. I don't know. Would I run in there? Probably not. I mean, if it came down to it, and the "bearded dude" had to prove that it was female, fine. I'm not personally looking.
I get that trans people have it rough. I do. But that's not my fault. And I don't feel bad about it. I have enough to feel bad about. I have enough stress in my life to not worry about whether Bubba the bearded lady feels comfortable swinging her dick in whatever the fuck restroom she chooses to use. And in real life, this isn't really going to apply to me anyway. So, fuck it. Swing your dick or throw your pussy out wherever you want to.