Mobs Vanishing On Restart Of Solo World

I play on the Caves and Cliffs Experimental build. I have a pasture set up with some livestock like Sheep, Cows, and Chickens. Yesterday and today I was making an iron golem farm and put all twenty villagers into their respective pods and finished the build. They were not spawning any iron golems only cats so I saved and exited. Upon rejoining the world all the villagers in the pods were gone and half my livestock was gone.