I know what you mean, but with all three of those players in that tight vicinity, from where the ref was at, he couldn’t have helped see the collision even though he knew the ball wasn’t there.
I think he simply had tunnel vision on the ball. And I am not bothered he didn’t call it. It was an incomplete pass. Heck, I think the game was still 3-0 at that point, but I don’t think it would have made a difference even if the call had pushed the Broncos back a few yards.
They didn’t have problems converting on 3rd and 15 or worse.