There is no way that was going to be overturned, his knee never hit the ground and neither did the ball. Even if it was very very close, it would have had to be overwhelmingly noticeable to overturn their original call, which it wasn't. If there is someway you can, you should look at it again.
I also don't agree with the posters who say he should have challenged the play based on the moral of the team. Since his knee never hit the ground, and it wouldn't have been overturned, wouldn't that be worse? First, the players are dropped to a low because of the fumble, and instead of going right back out there for the next play, they hold hope for a few mins that the call will be overturned, only to be taken back down when it wasn't.
Good job by DJ and the guys looking at the plays upstairs.