This demo came on sale a few days ago on Yahoo Auctions, and I won it today for a tenth of the price!From the Wild Optimism department:
C'est La vie "not seen her SINCE" demo, 90000Y
https://www.mercari.com/jp/items/m84478805948/
I wonder if the recording of the song is any different than on the omnibus.
If it's different, I don't mind sharing it if anyone's interested!