I don't think it's forward, it looks like it was thrown at ~26 and it hits at about the exact same yard line, but it's close. The L is certainly signalingly it's backward and live.
But I think this is a case of common sense over the letter of the rule. Once FSU had it and players were streaming on the field, the game is over. Even the ND guys had quit, no one was trying to tackle the defender with the ball. The R sure thought it was over, he was 20 yards past the U and the L headed off the field!