Villagers continue to disappear in the daytime

On my Minecraft world I was trying to get my stuff back because I forgot to turn of my device before I went to sleep. I went of to collect some wood to make sticks for the fletchers, but when I got back all the villagers were gone except for a child and a fletcher. Later the fletcher disappeared and child grew and became a fletcher, so I went to another village to find another villager to fix my village back up. I did that it was all good until I went to go craft the wood I just into sticks, I turn round the corner and the fletcher was gone so I was just left with a farmer (They disappeared in the day and I was also play with my Xbox controller on my device).