Can you find a thermometer to check to try ensure the temperature is 99.5 or as close to that as you can get?
I had one the other day pushed out of a nest the night before, unbeknownst to me. It fell 2.5 feet onto a hard wood floor and by some miracle didn't break or crack. It was iced cold as the temp that night was 50F. I put it in the incubator and next day it hatched. It's out with it's mom now after two days to recuperate as it had a tough time standing for a while. Probably from the crash.
This chick beat all odds, so it can happen!
But, there is a chance though that your hen just took an extended break. I'd see if she goes back to the nest, and if so, I'd give them back to her.