I would declare that in this day and age it is unreasonable for the writer of the writer here to assume that the person to whom they are speaking is female.
I imagine it all started with some dude at the beach saying, "Hey bra! Come check out this movie with me!" and the Bra said "Right on!"
I encourage the movie theater worker to try surfer lingo with the undergarment in question before giving up all hope.

When did Sean Hannity start seeing movies in Seattle? Who would have guessed?

@1 is it unreasonably? I mean only 99.5% of bra-wearers are female. It's nearly 50/50!

Isn't this too unique a situation for I Anonymous?

It's not unique!! I once saw a bra on the balcony rail at 5th Ave Theater! Lights went up and there it was. It was bewildering. Now I know it's a "thing."