I don't know if anyone will believe me, but. About two years ago my brother's friend (lightskin dude, curly hair type that girls flip over) was dancing in the club in Hollywood with some random brownskin girl. After the song ends she turns around to face him...and it's Rihanna.
The dude gets around with the women but to hear him tell it, when he realized who it was he froze up and was tonguetied. She walked away and that was that.
If this sounds farfetched, consider that if you've partied in LA or Hollywood you know that sometimes celebrities just pop up at different spots. Rihanna especially is known to just hang out in different places and be cool to talk to.