As the ball was being recovered (or downed, thus ending the play) at least 30 of the ISU players and staff were already on the field celebrating. By rule, the refs should have thrown a flag and we should have received an extra try, half the distance closer to the goal line. I remember a FBS game earlier this season where the team/fans rushed the field early during the middle of the play resulting in another try.
Let me be clear to say that I am not complaining that a flag wasn't thrown, if I was a ref I wouldn't have thrown it either, I'm just saying that by rule a flag probably should have been tossed.