Villagers disappeared after game save

I could not find a dup issue. 

 

I spent 6 hours yesterday rounding up 50 villagers for an iron farm. I set them up one at a time. (Villager named, bed, work station, trade.) The world was saved and reloaded as we have SERIOUS lag issues. Come to the world this morning to find every one of them gone. I am on peaceful but have NEVER had them disappear all at once. No chunk border. No hostile mobs can touch them.