Welcome to FT, assuming we see more of you.

It's a shame you didn't research your lounge entitlements before you traveled or you would have avoided disappointment. You'd have to be at least a Silver tier member or flying in Business or First class to have lounge access. I think you'll find that nowhere in the promo materials for your credit card did it list lounge access as a benefit. And to be honest, if you don't fly enough to at least hit SL or spring for a premium-class ticket, you're not one of their "loyal customers," so it's not surprising they wouldn't make an exception.

In future for a layover of that length you should look at hotel options near the airport, or one of the pay-in lounges. And as for "ruining your Christmas," I think most people will agree that in this case that's mainly a matter of one's attitude, not the airline's actions.