SINCE yesterday was Secretaries' Day, the near impossibility of getting anyone's secretary on the telephone was understandable as they were all being deservedly pampered by their bosses. But we thought a certain managing director of our acquaintance (we will spare him blushes by not naming him) had chosen quite a novel way to mark the day. When Keeping Posted rang to speak to his secretary we were informed that ''she was tied up with the boss''. Hmmm. Bet she would have preferred lunch and a bouquet of roses to funny games!