dID YOU DEAFEAT Geosgaeno,that thing with the ribcage at the begging of the game?

if u havent got bahamuts sphere yet dude im srry but u will have to restart becasue u can
never go back to the temple and its only once but if u have got the sigil look through a
walkthrough ion youtube its the easisest way

get the destruction sphere treasures in each of the five other temples (bevelle is fine
cause u cant leave that temple without it) then activate the statues and pick up the
goodies in the 2 chests (one of them contains 4 mega phoenixs), good luck.

You need to get all the treasures in all the temples and you have to go back to zanarkand
ruins and do that trial again