I'm going to try to come up with an answer here, but I need some information, because I don't have access to my copy of Missing Adventures right now. Is Terra Incognita a novel or a short story? And if it's a short story, do you know if the complete short story is posted in Missing Adventures or not?
Basically, if it's not complete (either as a novel or short story) it could only be covered as an unproduced story. If it is complete as a short story, we will have to discuss it. (As a first guess, I would think we could include it as we do for the one valid DWU story in Decalog 5: Wonders, but that's just my first impulse.)