There are some items, like the Diagram (for crafting) of Draug' s Confession, that are found in game files, but are actually unobtainable in game. Is there someone who knows for sure, and could possibly provide official info, first of this certain sword (Draug' s Confession) and secondly of other similar items (that are present in data and ingame not), concerning if and how they can become obtainable?

Thanks in advance.