This happened to me on Singleplayer as well. I had a donkey with a chest with a level 15 enchanted book inside, and after closing and then reopening the world the donkey was gone.
I have tried in survival mode. Still no action.
It also happens on singleplayer.
Sorry, this isn't a bug.
This happened to me on Singleplayer as well. I had a donkey with a chest with a level 15 enchanted book inside, and after closing and then reopening the world the donkey was gone.