As frustrating as this situation sounds, and my comment is going to be, it really sounds like the responsibility lies with you on both counts. In my experience, once you leave the ship all bets are off. If you had questions about your folio those are best handled in a face-to-face format. You step off the ship and 5K new passengers enter...you are history to them. Keep a close eye on your cc statement and if you find something that looks fishy then I suppose you might be able to address it through your cc company.
I hate that about your luggage but as stated by @HipHipOnAShip it's likely gone for good. The luggage and everything at the pier is generally handled by a private company. Other than putting you in touch with them, there's not really much MSC can do. Perhaps insurance will cover the loss? Best of luck...I know it's frustrating.