The following video starts a bit earlier than the previous NOS one (couldn't open the other either); if I am not mistaken the Piper Cub which was followed by the 172 can be seen at the beginning at the right edge of the video. Possibly the 172 crew concentrated (in hindsight too much) on the Cub and their position relative to it, not even expecting another plane nearby. In addition, the dark Cub appears far better visible than the Husky which somewhat blends into the background in comparison:
Two airplanes collide in the air and are stuck together ~ ViralVideoCenter