Villagers despawing with no trace of their disappearance

In my base I have build up a nice little village near my house so I can hear if any of them are in danger. Without a hint of anything I went to sleep and awoke to hear the sound of billiards hums was very quiet. I go to the house i built for them seeing that only 2 remained out of the 8 I had. I assumed that they had just got eaten by zombies so I went looking for them and they were no where to be seen. The place I have the villagers  meant if they were zombified, they wouldn’t be burnt by daylight. They also shouldn’t of despawn because I was well within the 180 or so despawn range of mobs. Where could they have gone?