Not to worry! You’ll meet people when you get there. Everybody’s very friendly. A lot of people go to hackathons without teams. So it’s perfectly normal to go around to people, tell them you’re looking for a team, and ask if you can help out. Hackathons will often run team-matching sessions at the start to help you meet people.
Pro-tip: Invite your friends to come to the hackathon too! That way you’re guaranteed to have at least one familiar face.