Oh and FWIW here's the piece I was talking about. Not a great pic but it's to the left of the brake line and it "clamps" the chain adjuster to the swing arm at the back. This piece was missing from the videos of the broken adjusters.
Also, I believe that the adjuster has a "step" in it that wouldn't allow it to go forward if it was installed correctly. Stock pic,
The small pieces hold the notch of the adjuster againt the end of the swing arm making it impossible for it to go forward or outward like they did in the two examples "Ed" gave.