Snake in hay storage

Alex and I were restacking hay yesterday to accommodate the additional hay we bought when - surprise! - there was a snake curled up behind a bale I pulled out. I, calmly, said,"SNAKE! Snakesnakesnakesnakesnakesnakesnake." and hightailed it out from under the hay shed.
After some investigating (it's probably a rat snake), Hayes handled it and released it near our woodpile by the creek.
Alex said the snake was just doing its job keeping the place free of mice.
I said,"Well, I saw a mouse nest." "Did you see any mice?" "No," I said. "Then it was doing its job."
Our hen was trying to go broody and laid a bunch of eggs in the hay shed too but we discovered something had eaten them. Alex thinks it was the snake.