If you have a live trap, set you one with one of those dead chickens in it, may not catch anything but it couldn't hurt. never hurts to invest in a trail cam near a coop either.
I'd stay away from the feather fixer and check the feed good along with the containers.
I'm sure you will keep a...
Wasn't any old cleaner or anything of that sort in food/water buckets? If you pull one off the roost and handle it a little does it seem ok? No thermometer that Could have busted?