So called Chase, explained what had happened, and was denied by the customer rep. So asked to speak to a supervisor who was able to adjust my account and give me the additional 9% cashback as a one time courtesy since I've been with Chase since 2007 and had a good history with them.
All of my other purchases went through fine with the 10% cashback. I think it is because I waited until December 31 to place my order. I can understand the post date of January 3, 2016 but they changed the transaction date to January 2, 2016. So check your account if you ordered anything from Amazon on December 31, 2015.