I have a survival player world (not a realm) and I had 2 farmer villagers in a home I made, it was secure of mobs, light very well, and had iron doors, I went caving and came back to check on them and they were gone. I have a librarian villager in a different home which was still there so it was just the 2 farmers that disappeared.

edit: updated to 1.17.32 and loaded the world, they’re still gone.