I just did a little digging and according to Autoblog the GT500 was rescheduled to the Palm Beach auction due to Carroll Shelby having a "cold". What a load of horse crap. I watched that stupid auction for what seemed like an eternity to see that car and then they just decide to reschedule it at the last second without a word.
We asked around, and the official word from Barrett-Jackson is that Carroll Shelby caught a cold in the last few days and was unable to make it to Scottsdale. Since both Ford and Shelby wanted Carroll to be there when the car was auctioned off, the sale was rescheduled for the Palm Beach event in April.