All of the mobs despawned

All of the mobs near my base area despawned, a bunch of villagers with locked in trades, named mobs like cats,foxes,and turtles, as well as named hostile mobs. I think it happened when my iPad shut off because I had to do something, I was in my trading hall trading with a villager, came back after five minutes turned my iPad on and all of them had despawned, I walked around the area and noticed none of the previous mobs that I had had disappeared.  As mentioned before even the named mobs despawned. I thought maybe it was a glitch and I just couldn't see them(that has happened before) and saved and quit, but none of them showed up