If you're really interested in this sorority, you need to go to this event. This is their last recruitment event, right? Even if they have more, they may fill all of their spots. If you go and your friend isn't there, it will definitely show the girls in the house how interested you are.
Go.
ETA: I didn't know anyone when I went through open recruitment, either. Guess what? I got to know them on Bid Day! Go.