Help finishing Kingdom Hearts :(

Ive just returned to Traverse Town from Hollow Bastion and I'm stuck!
According to Cid, I need a G-piece he hid in the Secret Waterway
in order to get back to Hollow Bastion...can't seem to find it, though O_oI've consulted a couple of walkthroughs and they say something about going up to the sun mural.
Tried that and nothing happens.Please tell me what I'm doing wrong.

did you go to the sewers? if you talk to Kairi there's a wall with a sun on it. Go up to that and use it, done.

Yeah, the sun mural in the Secret Waterway. Talked to Kairi,
went to the wall, and...nothing happens.

o.O does it not give you an examine option? odd... i dunno then sorry. It should change to a moon when you get it done

Yeah, I don't see an 'Examine' option.
Can't even lock on anything when I'm in front of the mural.

There's something wrong then, all you need to do just go to the mural.
There will be an event with Kairi and you'll receive Oathkeeper.

I didn't really get what happened back there, but whatever the problem was, restarting the PS2 solved it. O_o

Replying to #7

Might be some disc error, enjoy the game now :)