He stepped into the street to get a better view of the bars, scanned their tattered awnings and tawdry lights looking for some clue? In his swank apartment on Leavenworth Street where Russian Hill drops to the flat expanse of North Beach and finally to the San Francisco Bay itself, David Courtland sat hunched over a series of routine reports, a week's file of technical data dealing with the results of the Mount Diablo tests!