You can't. It's completely and 100% random. If it occured before, then it was a fluke.Originally Posted by Fantasy Lover
If someone had done it before not randomized, they would have said something and offered a guide, or some evidence. As far as can be seen, there is nothing like this in the game at all, and the Treasure chests are completely random or empty (empty at random).
And no, this is nowhere mentioned in ANY reliable FFX guides on the game.
This is like LotRish on Ash Terrain; no one does it for a reason.