The play in question starts at around 1:37. I can't see where the side judge throws the flag. To me, the side judge appears to be looking into the backfield, and not at the WR/DB battle in front of him. The side judge then appears to casually jog back toward the line of scrimmage as the feed switches to a different camera.
Did I miss it? Everyone seems to agree that the flag was thrown by the side judge, and that he dropped it near the sideline, and that it was not a late flag. But I can't see it in this footage. Perhaps there is some other footage somewhere that shows the flag being thrown?