Removed door catch and the unthinkable happened...HELPPP

So working on my passenger 66 dart sedan door, not closing right. Was told to remove the door catch and check the door. So as I removed the door catch.....the threaded backing plate slipped right down, and is now resting at the bottom of the pillar. Please give me any suggestions that might help me get that thing back into position. There is a small hole at the base of the pillar, which I enlarged enough to get my pinky in it, and I can feel the plate.
Now the car is not drivable, which is an issue because it is my daily driver.

I tried removing the back door to see if any access through those holes, and I can't really see any. DO I have to cut a slot in the pillar??? how,,help..