Well my, my...... thanks to Mr. Miraclepieco I have a *much* better understanding of where that mystery part came from. Since there are two pieces in the picture that look like the one that fell out of my door, and the one in the middle feels to still be intact, I’m going to guess it was the part to the far right that is attached to that corrugated metal strip that serves as a guide channel for the window. That’s probably why the corrugated strip got caught up in the scissor mechanism because it had nothing attached to it to keep it out of the way. I also now understand why that corrugated strip went so deep down in the door. Apparently it is to hold the window steady when it is rolled down. That way it won’t rock back-and-forth. Looks like there is an identical channel on the left side of the window, so I am hoping that will give it enough support to not allow much movement.
Thanks Miraclepieco for the picture. The cutaway view couldn’t have been more perfect!! I’ll be on the lookout for a cheap borescope camera. I can imagine one would come in handy in a few places on my truck, like while underneath the dash when I get ready to install my refurbished gauges.