Wow, somebody is very confused. Thanks for the pictures, it actually looks like my piece except it folds. The forgot to put the piece which runs perpendicular to the floor and behind the seats for the panel to sit on.
I also think that they have it backwards as the edge with the lip should mate with the standard rear panel and remove the current gap which I have.
Now what is the SC's next move?
beths11: I actually showed the Sunnyvale Service Center techs your picture of the rear flooring as it is installed in your car. They were dumbfounded and had never seen anything like it. Ouch. I thereupon hounded them mercilessly about how the Tesla folks in Oregon could get things done while 20 miles from the Fremont factory everyone was scratching their heads. They took it in good humor, but I have not heard from them since Thursday's experience, despite being told they would quickly clear things up and call me on Friday. I'm old enough to know that was not likely to happen.
Gwgan: if they still have the folding shelf piece when I go back, I will try to get it for you. You are absolutely correct: it was the upper shelf for a Model X signature edition.
On a more positive note, I spent yesterday driving up to Squaw Valley from San Jose CA through rain, sleet, snow and hail. While I delivered no mail to anyone, it was a wonderful drive in a Model X: great traction through everything and definitely fun. Plus, there were Superchargers right there in Truckee to nuke up my batteries for the return trip home.