91 LX 5.0 Hatchback door striker back plate fell.

You have to access the back of the door jamb which means you'll have to pull the lower back seat and remove the trim panel, there's a little more to it IIRC but not hard, lots of screws, some different lengths so pay attention, you should be able to reach the inside of the door jamb. The plate rests on some tabs at the striker hole.
If it will not stay in place, broken/bent tabs, I dab a bit of RTV and assemble the striker and adjust the door.
This is from memory and is a little dusty.