Kimahri's Ultimate Weapon

[Rizzice]

So I was going for his ultimate weapon in Thunder Plains or w/e.. by saluting the 3 cactuars statues.. after this, I observed the broken tower like the walkthrough told me to.. a chest appeared.. but when I tried opening it it said "It won't open."

What's the matter here? Was I supposed to pray to the statues AFTER observing the tower? Hmm

EDIT: Rikku's chest is not opening either.. it prompts the same message when I try. Maybe I am not far enough in the game for it to allow me to obtain the weapons? I just finished Zanarkand and obtained the airship, and was trying to complete some objectives before entering Sin..