On the same day that she sent a Happy Birthday @chrisbrown tweet to ex-boyfriend and abuser Chris Brown, pop superstar Rihanna blew off her SNL dress rehearsal – an unprecedented move, according to TMZ.

Her simple tweet provoked a number of tweets suggesting that she's gotten back together with Chris Brown, as the rumor mills have been saying for quite some time:

And that's not the only reference that Rihanna made to Chris Brown's birfday. Earlier in the day, she retweeted a fan who remarked that her remix of Brown's Birthday Cake reached the top position on the urban radio chart on Chris Brown's birthday:

Meanwhile, Rihanna missed her Saturday Night Live dress rehearsal in front of a live audience, angering producers, according to TMZ.

According to our sources, TMZ wrote, RiRi called in sick for the dress rehearsal, which is done live in front of a studio audience right before the actual show. We're told Michaels takes dress rehearsals very seriously and was quite upset when Rihanna bailed at the last minute.

But when she showed up later looking just fine, the staff got angry. But apparently Rihanna is enough of a star to get away with it, because no one from the show called her on it, according to TMZ's source.

Meanwhile, Rihanna's camp denied that she had just blown it off for no reason, insisting that she was in the building for the dress rehearsal and simply felt too ill to do it.

TMZ continued, bizarrely: We're told RiRi had a doctor come to her dressing room before the show and administer a shot of penicillin before she went on. ...oh?!

But lest people think that Rihanna was on a secret rendez-vous with former boyfriend and abuser Chris Brown, he was supposedly partying it up in Las Vegas at the Las Palmas resort with nominal girlfriend Karrueche Tran, according to the Idolator gossip blog.

Back in February, Chris Brown send Rihanna a happy birthday tweet, referring to her by her government name, Robyn Fenty, which she thanked him for in a tweet reply. So maybe Rihanna was just returning the favor?