I'm not a conspiracy theorist, and I don't think the Lions were intentionally robbed.
Obviously, the NFL did not think it was a reception. Obviously, most fans think the NFL is wrong, myself included. I think the rule is not clear, and even if they go to great lengths to spell it out, the rule is ridiculous. To me, there were two separate motions:
1. He catches the ball, his butt hits the ground.
2. He rolls over on his way to getting up and drops the ball as he is rolling over.
After #1, to me it's a touchdown. The initial jarring of him hitting the the ground did not cause the ball to pop out. Which indicates possession. To me, and most other people.