I tried posting this on r/askSeddit and I think it got flagged as spam. Plus, there's not nearly as many eyes over there.

I was at a show last night and saw this cute girl HB8. Flirted a small bit during the first act, and then went and sat down and chatted up her friend afterwards. First girl comes up and introduces herself, and then runs off with one of her friends. I leave her set of straggling friends and go chat up a few other people, intending to come back to this HB8 (who is constantly standing with an obvious AFC) later in the evening. When the second band is finishing, I'm about to approach the girl when my friend tells me we gotta bail, he's got the runs, and I'm his ride. So, this was my first time hanging out with this crowd, so I don't know when I'll run into this girl again, but I have totally found her on Facebook through the event page. Is it too desperate/weird to send her a short message and friend request saying something like "Hey, I meant to run into you again at the show, but I had to bounce." and so on?