Thanks for everyones advice. I was able to find one of the missing chickens the next morning (she was hiding in the front yard), and the other one was hanging out by the coop when I got home. The other one (that the snake had in its mouth), her face has healed.
We have left the outside...
New to the forum and keeping chickens. Found your site this morning while searching about snakes. Last night a big black snack got into my coop and was trying to eat one of my hens. I thought she was already dead, but apparently I got to her just in time - her face is a bit scratched up...