Can anyone Identify this little item and where it goes?

I remembered having left this bit off one side when reassembling side interior trim back on the car. It's pretty distinctive so I probably figured there's no way I'd forget where the heck it went. El wrongo.

This is off of a '99 S70 that I have just about ready to get re-registered and back on the road. Basically because I could, it's spent a couple of years in the garage in various stages of disassembly. I've had the dash out among other items, doing repairs on the cracking mounts. Tackling various maintenance items and upgrading the audio, adding power sockets, switches, etc.

Most of the less common fasteners I had grouped together in bags or bins but some still elude me as to where they go. This one I had thought went in the B pillar area down towards the bottom. At least that is if memory serves at all. I pulled both B pillar trims back off in an effort to see it's analog part installed somewhere. It probably goes under carpet somewhere along the rocker panel.