I would just return it for a refund based on their policy.
Guarantee, Returns and Exchanges: Costco guarantees your satisfaction with the merchandise you purchase from us. Costco.ca merchandise may, subject to what follows regarding diamonds and certain electronic products, be returned to any of our hundreds of Costco warehouses worldwide. Or, if you wish to return or exchange merchandise directly to costco.ca, contact us at www.costco.ca/customer service. When returning items containing a 1.00 ct diamond or larger, Costco warehouses may require additional time to verify the diamond, in which case a refund will be approved upon positive verification. This process may require 2 to 5 business days. Televisions, projectors, computers, cameras, camcorders, iPOD / MP3 players and cellular phones must be returned within 90 days of purchase to qualify for a refund. For more information on Costco's Electronic Return policy, please click here. Costco may in the future restrict its return policy regarding other products. Restrictions will be shown on the corresponding product description page.
The packaging always seems to advise you not to return items to the store where you purchased it but to call the manufacturer. You of course are under no oblogation to do that.