My sister in law is French. So is the wife of one of my best friends. They are both lovely people.
This kind of comment either shows up either your own ignorance, or that of your client, rather than that of the restaurant staff.
Your client ordered you a well known, however divisive French dish, possibly to obtain a reaction from yourself. It was either done deliberately or your client wasn't very well versed in 'Paris Talk'.
If I was waiting on you, and you wanted to send a dish back to the kitchen simply because it wasn't what you thought it was, then I would happily oblige, but you would be paying for two meals instead of one.
Did you have to ask your 'Paris Talking' client what the tall pointy iron structure was called, and did you trust them enough to tell you the correct name?