Yeah, you may have a point… Except that they didn’t rule an incomplete pass on the original on field call. They ruled a complete pass. It definitely was not that. As you say, it slipped through the receiver’s hands. That much is clear in the video. As such, it was either an interception or an incomplete pass.
So, if the bombers challenged the ruling of down by contact, I think the video review conclusively showed that the receiver never had possession of the ball. Hence the call on the field should’ve been overturned.
Unless I am missing something? Which, unfortunately, does happen from time to time. 🙂