This is a bug I’ve been noticing for a while, and seems to still be present in .8: sometimes, when convincing an NPC to give you an item, you’ll succeed, but the item will be nowhere to be found. Not in your inventory, not on the ground, nothing. It doesn’t ALWAYS happen, but I’d say it happens more often than not. Has anyone else experienced this?
NPC’s are currently rather buggy (which is why we are planning on making them our upcoming focus). Things like this are all too common, sadly.
Okay then! I just wanted to make sure somebody knew about it!
Yesterday an NPC gave me a bear trap that transformed into an electronics skill book in my inventory heh. Yeah fixing NPCs would be a great focus for 0.9 
I suspect this isn’t actually a NPC specific bug, but an inventory-handling bug.
Basically the inventory letter shifts out from under the NPC, so it gives you either the wrong thing or nothing.