Thank you for all your replies. Delta did refund the unused portion of the ticket and I've also received a bonus of 7500 miles as a good gesture.
Jordyn, I will try to submit a claim to Chase, as you've suggested, but I'm not optimistic. I've saved Delta money (they would have covered my hotel in MTJ and then in ATL the next day) and all they could offer was 7500 bonus miles.