That`s the first I heard of a Mirror falling off like that. It lasted 30 years out in the elements so probably much longer than the MB designers anticipated.
The only one I saw on Pelican is for the left side.
1983 Mercedes-Benz 240D Sedan - Exterior Trim - Page 2
Next time you are in the Yards, use a flat Wedge from the outside edge of the Mirror, and pry it off. the outer end is held on with a Ball/Socket and the inner part is a flat forked piece. Pop the Ball and pull it off.
The whole Mirror assy is around $35.
Charlie