If you did stop, go to court.
If the cop shows up, it's going to be you versus him. Tell the judge you always make it a point to come to a stop, and you do recall stopping at that very sign as you had seen him there all morning (why would you be so stupid as to break the law in front of a cop that had been there all morning?!). If he dismisses, then you're set.
If the judge notes that the police are more believable than you in this case, enter into evidence a copy of the San Francisco Chronicle article by Peter Keane, a former San Francisco Police commissioner, who wrote of a police culture that treats lying under oath as the norm, and note that the ticket you received was on the second-last day of the month, when police are actively looking to meet performance quotas, explicit or implicit in performance reviews.
...or ask a professional lawyer instead of an amateur armchair quarterback (me) on a Tesla message board.