If all depends if the casino in question has posted -- a letter of redemption notice -- concerning the strike or strikes in question. If the letter has been posted and the time limit for redeeming the strike has passed. Then the casino does not HAVE to redeem the strike. If no letter has been posted on the strike or strikes in question then the casino in question HAS to redeem the strike or strikes at face value. As I understand the NGC rule on this.

If I -- remember right -- the Stratoshere has posted this letter on all their past silver strikes. I am not sure about the Treasure Island but seems that I heard they had posted this letter.

Maybe someone else can confirm or not confirm this.
Dan