So, the poor customer service experience at Cold Stone Creamery that prompted my complaint to corporate has resulted in:
a personal call from the store manager, where he apologized and offered to accept my coupon if I wanted to come back even though the coupon is expired, and has reprimanded and grounded (temporarily laid off) the offending employee;
an email from the regional manager, apologizing on behalf of the company;
and a new coupon for one of anything I want at any Cold Stone.
While I don’t have any plans to go back (their ice cream is just meh), I feel the company has done a fine job of apologizing and trying to appease me. I hope the employee actually learns something from this; poor customer service is such a big no-no.