Great thread Ballardbeau.
The Diptyque scent that your looking for is *L'Autre*.
I would pretty much characterize my experience along the same lines as yours. However, if I try a fragrance, even if it's a sample, and I sit down and explain it to myself, that is, I explain what it's doing, what's going on scentwise, it's pretty much locked in my scent memory, and I can identify it again pretty much 99% of the time. Once, I start wearing a fragrance in full-on spray mode, it's in the database for good. I also have a facility for being able to remember faces, names, tastes, and style in art works, particularly in painting and sculpture. I think this helps when it comes to remembering scents.
Again great thread. I find the whole brain/smell connection mechanism fascinating. I certainly think, like most things, one can train oneself to remember scents.