I agree with some of what Accension said, disagree with some. Definitely as he said work on building up your personal network of go-to contacts to figure out where the party is at or where people are hanging out at.
That said, with the girl at hand, I disagree with Accension and say hang out with her some more. Send her a message on Facebook saying something like, "Hey, I had a fun time at the party. Let's grab a cup of coffee on (whatever day you're free) and hang out for a bit." Do NOT refer to the hookup unless she brings it up. You're not being ****y/funny by doing so. Trust me. It can be done, but not easily, and frankly, there is no need to at this point just over Facebook. You can be ****y/funny over coffee--in person.