I took a few pictures that I hope will help.
Two of the three retainers are just flat plastic stock. It appears these are there to prevent door from lifting off.
The third retainer (sort of "C" shaped) is the one that keeps the door from sliding sideways on the hinge. I thing this one could be more square shaped (or tapered) and still do its job as long as it fits into the notch in the door panel so the door cant slide, and clears the curve of the hinge.
When I removed the door, the little (#6) screw broke off on the C-shaped retainer. I'll need to drill that out, or use a different location that aligns with a notch. The other retainers came right out. I think they were the ones removed when the door was taken off at the body shop. It may be that the C-shaped one doesn't need to come out to remove the door (it didn't look like it was ever out). I'm not sure.