I could just be an idiot, but I'm having trouble. I beat the Sanctuary Keeper on the first try. I went up the path, got to an area where I couldn't run, only walk. The map disappeared, and I was on an uphill slope with Lulu, Auron, and Yuna. I can only go so far on this path forward or backward. I couldn't figure out what to do, as I can't talk to any of the others. I restarted, then beat the Keeper again. This time, I went back to the cave and saved so I wouldn't have to fight it again. I did a more thorough search in the battle area, and then ventured onto the path. Same thing.
Supposedly I am supposed to find a sphere from Yuna? But I don't see one anywhere. My volume is up loud enough, so I would've known it if I had triggered it.
What am I missing? What do I do to continue?