Does CC know that you opened it and used it? If so, you just 'rented/borrowed' it for $75 for your trip.
If they don't believe you've opened it, they may go easy on you. Just tell them it was a gift for someone else and they didn't like it, or maybe you received it as a gift and maybe they'll hook you up with an in-store credit...without charging you 15% restocking fees.