Remember someone once mentioning something about being able to get the quest items to drop from bag. Don't recall the exact steps, but from the top of my head it couldve been something with filling up the backpack (125 items), and then crafting one item, while holding the quest item with the cursor. Then try to drop it in backpack, which is now full because of the crafted item, and might make the item drop to the ground under your char.