Hello, as brocéliandre said, please check the Hoard, a menu accessible through the button in the upper right-hand corner of your Main Screen -
http://prntscr.com/4q52jw. All the caskets you receive throughout the game are stored within the Hoard, including the caskets for Barbarian Camp destruction. If the rewards are still missing, please write the date and time of the battles against the Barbarian camps.