No, Catsmom, look in the corners, near the waterfall (not in the waterfall itself). If my memory is correct, the one I had trouble finding was in a corner at the front of the cave (where you came in) on the left side. I got up by the stepping stone, and hugged the wall all the way to the front. I had to go into the corner smack into the wall to engage it. Is that the one you're missing? I remember it took what felt like forever to find it. Just try sticking to the wall as best you can, using the conch to call it.
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"How could drops of water know themselves to be a river? Yet the river flows on."
- Antoine de Saint-Exupéry