Think of them like preschool age children... Curious, smart, hungry. Can and will climb fences and trees, even buildings, pull, rip, tear, claw fencing, dig under coops, open latches, escape traps.
SMART buggers, everywhere. They hide extremely well and you would probably only see evidence... Torn feed bags, garbage cans, footprints in mud, especially...
Water, they LOVE water. They have to "wash" everything they eat, so look for footprints around mudholes.
Best bet is always locking up at night and predator proofing to deter a kid