Has anyone used the Carnival's onboard coupon booklet ? There is a coupon for a free work of art if you attend an Art Auction. The art work is to be your choice and valued up to $95. When we attended the auction we were told the coupon would not be accepted. These coupons are offered by Carnival through certain travel agencies. Also offered to past guests. Has anyone else had a problem with the ships accepting these coupons?