Door panel 2000 Toyota Sienna part fell out

I removed the driver door panel to attempt to replace the driver side mirror. When I removed the panel a piece fell out. I attached a picture. Here is a link in case the attachment doesn’t work. It isn’t one of the little clips that come off fairly often when removing a panel. I don’t recognize this piece. Anyone have any idea what the piece is? The door is back together and all seems to work, but I can’t imagine it being an “extra” piece that isn’t needed. I took the passenger panel off to look and couldn’t find a similar piece. I know the dealer has had the driver panel off a couple times to do work on the window motor. I tested that power window and it still works though so I am at a loss.