What was he thinking?

[mauconnfan]

I think this is the case:

It's a rule that no one seems to like or get. The receiver has to control the ball all the way to the ground. So in this case, even though he knee was down and he had control, because he didn't keep control when the rest of his body contacted the ground it was incomplete. That would be why they didn't challenge - because even though it looks a like a catch and common sense tells you it's a catch - by rule it's not a catch.

Thanks good explanation and hence why they didn't - yes it is ridiculous because he had possession. Rules are rules nonetheless so I get it!