you could also argue if the credit card company had refunded him his money then the 4m is theirs
I think you'd have to do a better job with your argument than that. Sure, the card owner isn't out of pocket, but it still wasn't these guys' money that bought the ticket. If anything, your point more points to the credit card company being the rightful claimants of the 4m as they effectively paid for the ticket if they've refunded his money.