I will be surprised if F9 refunds. Even AA is now at 4 hours for "significant" change and that is what triggers a refund under the DOT rule and a chargeback. The card issuer will only issue a permanent credit if the merchant acquirer is willing to pay or the card holder is a very, very, very good customer (meaning that the card issuer eats the refund).

If F9 won't refund, OP will need to sue F9 on the grounds that the change was "significant" despite F9's policy.