What are these pieces inside my door???

I pulled the front interior door panels off my car this evening to reaffix the map pockets and arm rests. Thanks to the forum for previous posts that made this a relatively easy job. Only casualties were the clips at the top of the side mirror covers. One was busted by previous mechanic, then I broke the other one tonight.

The previous owner of my car had been backed into on the left side. This was my first opportunity to pull back the interior panel to examine the repair work. Two questions for the forum:

1) Pulling the panel revealed a kitchen plastic garbage bag taped over the door. I didn’t have this on the right (non-damaged) side. Do drivers side doors normally have a sound barrier over the metal housing (in addition to the particle board on the interior panel)? Did I discover a cheap replacement?

2) The passenger side had some clips fall out when I removed the panel. They look like the below picture. I couldn’t find their function, even when comparing to the drivers side door. Any ideas? A similar looking clip was used to hold one of the panel hooks to the panel, but it didn’t look like the panel was missing any hooks.

My door rattles are reduced dramatically. Also, I plan to use Velcro to reattach the mirror cover, unless anyone has a better recommendation.