J´ai réussi avec du bol.
Fais une sauvegarde à part pour retenter au cas où.
Voici la tech de gamefaqs:
THE WHOLE THING IS TIMED ! !!
[...]
Counting begins when you arrive at the chest, NOT when you stop moving. Accuracy is critical, but not impossible. If you hated Chocobo Racing to get 0:0.0 using a timer, then you´ll hate this too. The exception here is, the prize is much more valuable!
First, the " Original Method" of counting:
1. Upon entering a room, note how many chests ( important)
2. Approach a chest and begin counting off the number of chests in the room, then OPEN
3. Go to the next chest and count off ( but now there is one less chest), then OPEN
4. Repeat for each of the chests in the room
Source : http://db.gamefaqs.com/console/ps2/file/final_fantasy_x_omega_ruins.txt