Reconnecting Rigid Dryer Vent Line
Ah, how I hate people who build things designed to last forever, or rather to need the house ripped apart when they don't.

I'd try a loop of wire (galvanized steel or aluminum, whichever the duct is, so they don't corrode each other over time) wrapped around the pipe in the hole to allow you to pull on that while shoving the stub pipe into the elbow. Look down through the stub so you can see what you are doing. Attaching that wire to the stub would then hopefully keep the elbow from falling off again. You would need to seal the joint with duct seal since there's no way you can tape in there. 

Alternatively, figure out where the access panel for this job should have been put, buy an access panel, cut a hole in the ceiling (below the pipe), and put the access panel there. Or do what too many folks do, and simply cut a hole in the drywall, convince yourself this will never happen again, and patch the hole in the drywall.

If you are having trouble mating the male and female bits, bend the male bits inward a bit more than stock.