Numerous reports placed a man who matched his description sitting forlornly on a Golden Gate Park bench in a downpour. A groundskeeper offered him an umbrella. Law enforcement teams searched the park for days and dragged the bottom of its largest lake.
The possibilities that Tang intended to disappear or may have killed himself remain open, though police efforts to locate him remain active.
"Mr. Tang did cancel an appointment that he had. He did say that he was not going to work," said Martin, the missing-persons detective. "When you hear that a person has at least a short-term plan not to do what he was going to do, you have to think: What was in his mind to make him not do something the normal way that day?"
But Tang's family and friends cannot linger on those thoughts. Psychics have pictured him on a street, lying in a garden, on a beach near a windmill.
His disappearance triggered a viral response as e-mail lists begat e-mail lists. A Yahoo listserv keeps 200 of his closest friends informed. Another public website -- www.findjerry.org-- draws tips and ideas from hundreds more.
Strangers, too, are spreading the word.
"This really has struck me," wrote one on a family blog. "This man is one of those 'upstanding' citizens, a good father and husband, a high-tech executive, a neighbor ... and then suddenly he is roaming the streets.... But for fate, there go I."
Tang's family is also humbled by the response.
The day after Jerry Tang's birthday, his father took the train to San Francisco and walked the gritty blocks past addicts and drunks to the San Francisco Rescue Mission. There, he prayed for Jerry and participated in a Bible study.
"You know, I talk to many homeless people," Jeffrey Tang told Pastor Ralph Gella and a small gathering. "Many of them express concern. They volunteer to show me around. Even though their physical condition is poor, they still have righteousness."
The session over, Jeffrey Tang asked the men if they had seen a volunteer known as "Boston." The man from Massachusetts had told Jeffrey Tang a week before that he believed he'd seen his son. But on this day, "Boston" was missing too.
With a laminated missing-person poster of Jerry pinned to his shoulder bag, Jeffrey Tang then made his way to a financial district building where Tang worked four years ago.
The company is long shuttered, and another has replaced it. But the security guard accompanied Jeffrey Tang upstairs so he could search the unlocked sixth-floor bathroom.
"It's a longshot. I don't know what I'll find. But I just want to be clear in my mind," the elder Tang explained.
"I am trying to generate some hope."