I opened a door card to get a leather color sample for a custom color dye and this thing fell out from the bottom when I pulled out the door card. I looked at a couple of youtube videos but I do not see it on other ppl's door cards as well. It seems like some window regulator part, can anyone confirm? The window seems to close fine but I would like to put it back where it belongs.

 

It's part of the door window weather striping.

I will try to find the part, hold on...

#72450-S2A-023 MOLDING ASSY., L. DOOR - you are holding #16 in the diagram:





DIY for replacement found here: https://www.s2ki.com/forums/s2000-mo...lding-1085317/

OP even mentions his "brush" was also missing on the old part:

 

Thank you!