Ok, yesterday I had a hunch.
I checked the trunk more carefully, and....
The large bag is for the Charging Cable, supplied by Nissan, and clipped into place where Nissan placed a ring it clips to.
(The stitched black blanket is a Moving Blanket from Harbor Freight. They sell for under $10, and are great for protecting the floor of any trunk. Probably help keep me warm, too, should the need ever arise.)
Now do understand - I only discovered this Kit existed at all by carefully reading the Owner's Manual.
The Salesman was unaware of its existence, as was the Service Manager, and the Parts Counter guy.