OK, sorry, I’ve just found it. It’s at the top, the first item. I was looking for it alphabetically, so at the bottom 🙂 (I’s so much easier to find things in a list that wraps horizontally rather than a long vertical ribbon 🙂 🙂 🙂 )
That is, as I mentioned above, not a place called “unknown” but a completely blank / non-existant place. Hence why it is at the top of an alphabetic list.
Best way to find it is using Batch update, as described in my earlier reply.