I hired a helping hand from nearby seal tribe village, then told the NPC to fell some trees using a handaxe which I gave him. I let him fell around 20 trees until I decided to kill him (stabbed in the legs with a knife, he fell to the ground, then in the head twice until he fell unconscious), killed him with a stab to the skull. After this I shut the game down (most recent Steam version) using task manager (I did not save).
When I loaded up the game again, the NPC was alive again, just unconscious again, so I killed him, but most of his items had disappeared. I know that he had a northern knife, the handaxe which I gave him, clothes and some food (I know this from the message log). All that was left were his woolen trousers and nettle cloak which had somehow been unequipped from him and were laying on the ground. I know that at some point during the fight he dropped his wielded knife, yet it too is nowhere to be found.