Thank you Maxima. That is good advice. It is good to know that most cruise ships and even airlines have been prepared enough to help you.
It is also good to know that NCL was very likely not negligent in this case. As you said, in amy cases the person may not even realize they are allergic to anything, and they als might ingest things, such as at a buffet, where they do not even realize they are eating a food they are allergic to.
Since I have a VERY mild allergic reaction to shrimp (and only shrimp, I have certainly chowed down on lobster and crab in much bigger amounts than I could ever eat in shrimp) I do watch out for it. But I will even more in the future.
As someone said, in a gourmet kitchen nothing goes unused. I would not be surprised at all to learn they use the shells and heads of shrimp to make a soup base, for example.
I know I will probably stop eating shrimp all together now. I don't think I need to chance anything like this happening to me.