This season, the Hidden Immunity Idol is on Exile Island so only those people who have been sent there could have it. The rules for the use of the idol this season state that it can be played after the votes are read, making any votes cast against the person who has it void.
Misty Giles was sent to Exile Island on the first day and she had told her original tribe that she had found it. After the tribe voted at Tribal Council,
Jeff Probst asked if she had the Hidden Immunity Idol, and she replied that she did not.
Misty Giles was voted off.