Did you watch the entire game? Earlier in the game they put the same hit on UGA's FB and 3 flags were thrown and then they picked them up and called no foul. Then after this call (which gave OSU a first down and then an eventual TD to put the game out of reach) OSU hit a UGA player again and they called the same thing and it was much worse call than this one (but the game was over at that point). The were clearly trying to make a makeup call, but it was too late.
If I was coach Richt, I would have gone Bobby Cox on the officials and got thrown out of the game.