My Costco receipt says 90 days, however, the contract I signed for Verizon states a 14 day return policy.
Right below you

All of the costcos around me (5 of them) have a sign posted that says ".....90 day return policy....." I would go in and complain. The 14 day contract is for the service..not the phone. You can only cancel your service before the 15th day, but you can exchange a phone up to 90 days.
Exactly