It didn't flop. But.. a lot of peole were confident that this would totally smash, but it didn't really happen. I think it's one of Rihanna's most overrated songs. If TTT was given video treatment, it probably could of done better.
Oh well. When Rihanna releases her next album, everybody will choose a dance song and hype it up for months until it's a single and we'll go through this all over again...
I think people should just learn to stop over-hyping songs all the time, but these people never learn I suppose. Some people just have short memories.