Could have been played up real well by Kelly.
Kelly - "Jeff, I've been holding this one since day 6 when I found it during a challenge. I'm safe tonight and so is Keith."
Shocked faces!
Kelly - "I'm voting for Jeremy and Keith is voting for Spencer. Tasha, you decide who goes home between the two."
Jeremy knows she had to find it during a challenge cause he found his during a challenge. If anyone asks if it's real. Kelly had the note for the idol as she kept it. Could they have called her bluff? Sure. But in a matter of 30 minutes or whatever from her reveal to the voting, they'd be crapping bricks right there. Would have made for a great tribal if Keith gets up, plays it and Jeff says, "this is not a hidden immunity idol" but one of Jeremy or Spencer did go home. All Kelly would have to do is get into the final 3 for the million after that move.