The phone call by Zodiac was completed at 12:40:30. Let us assume that Betty Main traced the call very quickly, at about 12:41 am. She would have done this in full knowledge of the seriousness of the call, possibly regarding four murders. So if she understood the gravity of the call and the need for police to respond quickly to the payphone at the intersection of Springs Road and Tuolumne Street, why did the police get the call from PT&T operator, Mrs Johnson, six minutes later? Are we to assume that they just sat on their hands for six full minutes. This makes no sense.
If the PT&T operators didn't ring the Springs Road and Tuolumne Street payphone, it is highly likely that the Zodiac Killer just made the story up for purpose. The Zodiac stated in his August 4th 1969 'Debut of Zodiac' Letter that "the man who told police that my car was brown was a negro about 40-45 rather shabbly dressed. I was in this phone booth having some fun with the Vallejo cop when he was walking by. When I hung the phone up the damn thing began to ring & that drew his attention to me + my car". It was the payphone ringing that drew the attention of the negro male, who conveniently noticed that Zodiac was in his "brown car" - without him, the Zodiac Killer could never have realistically informed us of these details without it appearing forced. The statement of "the damn thing began to ring" with the simultaneous expression of consternation that "he and his vehicle" had been spotted, used to make the narrative more plausible, when he had likely walked to the payphone that morning. No eyewitness to this call was ever recorded.
Finding the answer to the question of when the phone call trace was finalized and whether the payphone was rung back, is crucial to determining the movements of the Zodiac Killer on the morning of July 5th 1969. If he was in absence of his vehicle, then this would explain the forty minute delay from attack to payphone call, and narrow the search for our killer down to an extremely manageable number of residences around the intersection of Springs Road and Tuolumne Street.