"Unless you had wanted to gain entry to the First Class area .. then you would need to SHOW your QF Gold card even though it was obvious that you had it on your boarding card."

A QF Gold card would not permit access to the 1st class lounge though. Only Platinum and Chairman's Lounge members are entitled to that. As you said, with a business class boarding pass there should have been no issue anyway unless he was travelling with a carrier other than BA

Dave