I started playing earlier today and I feel like I remember seeing my mobs (specifically cows and Villagers) I realized all my cows despawned so I started trying to find new ones.

I then went down the mountain and realized all my villages disappeared. 

Some things of note, I am not sure if the all despawned when I loaded in today. Last night I was playing with friends. I am absolutely positive they did not kill the mobs.