I think I figured it out
Apparently a lot of people have been wondering about something:
Dunno if anyone saw, but someone on /vp/ found an item "on the PGL servers"
http://3ds.pokemon-gl.com/share/images/item/6fe339.png
Looks like a cookie or something. It apparently comes between Luminose Cookie and the fossils.
Kind of resembles a sub to me, or a boat. Although that doesn't make much sense being on a cookie.
Interesting find. I do think it's a cookie (although more like a cracker), and it does look like a boat.
Could it be a regional delicacy just like the Ragecandybar, Lava Cookie, Old Gateau, Castelia Cone, and Lumiose Galette? If it is, could it be from the backpacker's unknown region? Yet another XY mystery.
What's the item labelled "6fe339" (the dirt tile thing)? I don't recognize it.
It looks familiar but can't place what it is. It kind of looks like a cracker
I've been interested in the various mysteries like this in these games, and I've been attempting to see how dialogue in the game might shed light on some of them. This morning, to my surprise, I found a bit of dialogue that helped explain this!
I talked to a woman outside the Lumiose Galette shop, and here is what she said:
"The combo of Lumiose Galettes and Shalour Sables is the ultimate!"
(For the record, I do not know if having a particular level of style has anything to do with what she says, since I know that some other characters in Lumiose have different dialogue depending on how stylish the player is.)
Anyway, I looked up "sable" in the dictionary. No dice.
Then I remembered a culinary dictionary my dad has. Looking in there, I found that a "sablé" is a shortbread from Normandy! (Ironically, since someone thought it looked like dirt, I should also mention that it is supposed to have a "sandy" texture!) I have no idea why the game didn't put an accent mark over the "e."
Now, compare the design on the 6fe399 "cracker" thing with Shalour City's Tower of Mastery:
http://www.serebii.net/xy/photo/shalour.jpg
An even better view can be found by looking in the game. I think there can be little doubt that the design on the "cracker" is supposed to match the lopsided architecture of the Tower of Mastery, and it even has spots which seem to match the three windows. I think it is highly likely that the item under discussion is a Shalour Sable, as this explains the available data very well.
Now, if this is correct, I still do not know whether there is any direct way to obtain this in these games. It is possible that it will have to wait for future games to be released.