I was beginning to build my own NPC village. So I had been running around finding zombie villagers and reverting them to normal. I had only found one but I turned him into a villager. The villager was a farmer. I traded with the villager until he was master level. Then a day after that there was a thunderstorm. So he went to his hut and I went to sleep in my house. When I woke up to look for him he was no where to be found. I checked everywhere within 100 blocks of the village. He had always stayed at his work station and around the iron golem I built. I couldn't find him anywhere and think he disappeared. It might have something to do with me sleeping in a thunderstorm. There were no thunderstorms previous to this one.