I never noticed any Muzzie staff on the Celebrity or NCL cruise lines.
You mean you got to know them so well, exchanging information about religious orientation / confession, that you were able to "make a call?"
Honestly: Unless they are fair-skinned, brown-to-blond-haired people with names like "Sven" or "Gerhard," I don't think that you can be sure.
Regards,
We had a butler for our suite that looked identical to Obama....he was a Muslim.