Just an update. Hawaiian did give me a credit, but only for 1/2 of what they admitted they owe me. I've sent them several more emails, explaining and providing proof that all the credit to our credit card wasn't provided (and it was a significant sum). They claim I was fully reimbursed, to talk to my bank and ignored further emails from me. So likely I'll have to continue this fight via Dept Transportation and the Hawaiian credit card I used to book the fare.