Not the same situation but It reminds me of a young couple who bought a ticket from London(UK) to Sydney(Canada) instead of Sydney( Australia)...It was a cheap flight, they thought they were getting a great deal.
He should have been more careful of course, but to be honest I've never heard of place in US called Carlsbad either. By name alone it should be in some German speaking area... By the way it still happens from time to time that some clueless person ends up in the wrong Frankfurt (there are two, the other one being a much smaller town on a Polish border).