Poisoned camp and enemies disappeared

I was doing the first mission you get to kill some bandits from Sebastian. I sneaked in the middle of the night and put bane in their food. Afterwards I waited for like 9 hours. After the timer goes out and I load in there was only 1 guy sitting there. Everybody else is gone. Either they died from the poison and then their bodies despawned after the wait or that they just disappeared. I needed to loot their bodies for proof that I killed them. This activity can’t be finished without it.