Permanent 10% Chaos Res from the venom draught disappeared

I have completed the corresponding act 3 cruel side quest, picked the Venom draught of the lost as my reward, and confirmed afterward that my chaos resistance increased by 10%. However, I noticed a few days later that my total chaos resistance was a bit lower than I originally remembered. Sure enough, after unequipping all of my equipment and jewels, my permanent 10% chaos res disappeared completely and I don't know since when or what event made it completely disappear.



I tried re-doing the quest, but the corpse in the venom crypt doesn't drop another quest item.

Probably a bug? Unless this 10% chaos resistance isn't permanent?