I'm using Sharp steelbolts (heirloomed once) and I've ran into a following bug.
When I have no ammo, and go and pick up any other kind of bolts than my own sharp steelbolts, my char just drops the empty stack but gets noting to replace it.
But if I pick up again the empty bag of heirloomed bolts I just dropped, it turns out it's full again. I think this is pretty much the same as with the unlimited ladders bug.