Indeed HRH The Prince Philip, Duke of Edinburgh wore the Order of the Leopard (military), of the republic of Zaire. It's believed that the mix-up was simply caused by someone having mistaken the hand-writing of 'Leopard' with 'Leopold'. It was an honest mistake, but I believe the valet got a sharp talking to, or at least certainly recieved typed instructions thereafter.
I doubt that such a mistake would have drawn much attention from the other guests, many of who were wearing the Order of Leopold I. It was a rather unexpected death, and most would have been more concerned with HM King Albert and HM Queen Fabiola.