I would think that if it were removed for security reasons, they would have left a note. Then again, they could have a thief on their hands. I would call the aiport, and bring it to their attention. Question them on the acceptance of a kilt pin in checked baggage. If they say that it shouldn't have been removed for security reasons, then let them know that they might have a security person stealing from the luggage.
What airport was it? If you went through more than one, I'm guessing the departing airport would be the best bet.