Tap Tap Revenge 3 Achievements not registering?

I recently unlocked the Underdog II achievement (finally) and went to an online game. There were 3 or so people higher than me in level, and I came in first. I checked my achievements to see there was no indication I had beaten said players. Are they supposed to all be in one game? If so I'm screwed :P But if not.. why isn't it showing up?