After curing 4 villagers with a weakness potion (4:00) 3 out of the 4 had disappeared and one remained. 
Note:
The chunks were not unloaded
Villagers were renamed

They had not suffocated as they were surrounded by transparent blocks
They had not moved from the spot as it is impossible to do so.
After relogging they had not appeared, I also tried to imbuing villagers with glowing effects and they had not appeared.