I received this too. I e-mailed them and got the following response.

"Thank you for your contacting us.

We are sorry about the inconvenience you experienced with our store coupon. Due to an error in the mailing, some of the people who signed up for the promotion received the coupons too late to use them. We will be mailing another coupon out to you and we apologize for the mistake.

Robert
Consumer Relations
American Greetings Corporation"

I sent the email to: Consumer.Relations@amgreetings.com