I put a hook and eye on the inside of the door, so when I got in there when it's windy, I can lock the door shut behind me and they don't escape - I've got a couple RIRs who love to bang against the door to see if it will open. Anyways, this is the second time it happened, somehow when the door shut the hook did a loop-d-loop and locked! Luckily (or not, you'll see why) there's a big cleanout door on the backside of the coop, under the roosting area, that opens from the outside. Yup, I had to climb in through that door, across the yuckies, to get inside and open the door. Eeew! At least by the end of the day they've rustled the litter up enough most of it is covered.....
