Dissapering Animals

logged into my Hard survival to find both of my cats , my dog, all of my chickens , my donkey and my cows all gone. no drops to show they died, simply gone. donkey had a chest equipped and tied to a post, chickens were locked in a roofed pen and the cats/dog were sitting last i left them. Need my cats to keep creepers & Phantoms at bay, so i really need this looked into please.