Sorry to bring this thread back, but I DID find the inner door part inside the door. Yesterday I dropped some screws down inside the door and whil lookenig with a light AND a mirror-on-a-stick, I saw the piece lodged under the window bump stop at the bottom of the door. it was stuck in there and took a good deal of wiggling to get it out.
So yeah, your suggestion from 20-odd posts ago was the answer.
so, just wanted to say thanks about that.
Pete