Thanks OP for posting this. Pretty clear that the ref in the background (who threw the flag) of the video was too far into the sideline (almost 5 yards) and had a bad angle to see an contact. The ref in the foreground (right on the sideline who did NOT throw a flag) had the best view and should have disputed the call with the other ref.
That's part of my issue....refs huddle all the time to discuss calls ...and on 4th and 5 and possible game changing decision, you better make sure everyone saw same thing.