Removing door hinges... is there a backing plate behind it?

[CentralCoaster]

I have the lower hinge almost off, but it feels like whatever the bolts on the cab side thread into is loose.

Is there a plate back here behind the A-pillar similar to the backer on the striker plate?

If I pull these bolts loose, is that going to fall into the door and get lost?

I haven't pulled the fender, I'm just using my gearwrenches to get to these bolts.