got this from fox reality
Exile Island May Have Its Own Immunity Idol Clues; Jeff's Clue Was A Last-Minute Addition
February 7, 2006
by Andy Dehnart
During the premiere of Survivor Panama, Jeff Probst told the show's first inhabitant of Exile Island about the island, and then said that he'd just given her a clue. Dumbass Misty thought Jeff said something about the word "behind," so she dug around in the dirt behind where they were all standing, where the immunity idol probably was not located. But Jeff also mentioned the water supply and the fact that, without fire, it was useless.
As some astute viewers noticed, when the camera focused on the barrel of water, the tree next to it clearly had the letters Y and C written on it. (That, or the tree clearly has a vine that died leaving behind pieces that look like the letters Y and C.) Showing this seems deliberate, and could be a further clue, especially since Jeff mentioned that he'd given Misty her first clue.
However, Entertainment Weekly's Dalton Ross, who spent the night on Exile Island before the show started production, reveals that Jeff Probst's clue was in one sentence, which "was actually a last-second addition" and that, "Right before the castaways showed up, Probst and Mark Burnett were perfecting the exact wording, with Jeff practicing it over and over to get it."
Dalton, being a big cluetease, also says he knows what the clue means, but refuses to tell us, because he's mean. He writes, "Now, Burnett told us the meaning of the clue shortly after, but since spoilers are the bane of my existence, I will refrain from sharing it here. (Sorry.)"
Update: A reader reports that, while Jeff talked about the island's clues, a tree with the letter F on it was clearly visible behind him. While I don't have a screen cap of it, that seems to confirm that the clues are written on the trees.
http://www.foxreality.com/detail.php?storyid=3121&type=news