I'm sorry you're missing your chickens.
To clarify, this happened at night. You don't lock them inside their coop, and they free range and don't have a secured run, is that right?
If they weren't near the coop when the snow started falling, I can see them finding somewhere to hide until they feel safe to return to the coop. But to be gone all day today is concerning, especially with little to no food available to them.
Also, a predator could have taken them during the night, leaving no trace from what I keep reading in the forums. But with snow wouldn't you have seen tracks near the coop?
The injured hen perhaps sleeps in a nesting box and doesn't roost. That could explain why she wasn't grabbed; she wasn't where the others were when they were taken.
Please keep us updated. I feel terrible for you and your flock.