The tale starts when Sneddon, a 24-year-old Brigham Young University student who had completed a three-year Mormon mission to South Korea, was wrapping up a semester studying Chinese in Beijing in the summer of 2004. He had learned Korean and was planning to take a Chinese language class in his senior year at BYU.
"He'd gone to Beijing that summer to get a head start in Mandarin," his father, Roy Sneddon, said. "His course work was done, so he said he was going to take a look around some touristy spots in southeast China before he came back."
David Sneddon had been walking on an easy path in the Tiger Leaping Gorge, a scenic area in Yunnan province that borders Myanmar. He'd been to a Korean restaurant called the Yak Bar. And then, he disappeared.
His parents thought that their son, one of 11 children, had been detained by Chinese authorities. Roy Sneddon and two of David's brothers went to the area to investigate but found nothing beyond a suggestion that he had slipped in the gorge and died.
The case went nowhere until four years ago, when David's parents received a phone call from a man in South Korea who said he'd heard of a man fitting their son's description who was living in Pyongyang.
The Sneddon family had not considered the possibility of North Korean involvement.
But on reflection, there had been a strange incident. David had been approached in a supermarket in Beijing by a Korean woman who said her children weren't speaking enough Korean in China, and would he mind tutoring them?
And one of David's mission friends had been working in Yanji, a city near China's border with North Korea that has become a first transit point for people escaping. Was the Korean mother laying a trap? Had David or his friend been helping North Koreans escape?
"He had been associated with Koreans in two different ways," Roy Sneddon said in a phone interview from Utah. "The conclusion that we drew was that David had been taken, or kidnapped, if you will.
"We thought that his background and his language was one of the reasons for it."
Every now and then over the past few years, some Japanese newspapers would raise the possibility that David had been abducted by North Korea, an idea some in Washington saw as part of a Japanese effort to get the U.S. government to pay more attention to North Korea's abductions of Japanese citizens.
During the 1970s and 1980s, apparently under the orders of Kim Jong Il, who was then North Korea's heir apparent, an unknown number of people were abducted and taken to North Korea.
At least 17 Japanese nationals were kidnapped, usually from remote spots on the west coast, and taken to Pyongyang, apparently to train spies in Japanese language and culture.
A famous South Korean film director and a celebrated actress were picked up on orders by Kim, a movie buff.
Along the way, Thai, Romanian and Lebanese women were abducted. The Romanian, Doina Bumbea, was taken in 1978 and not seen again until 2007, when she was spotted in a documentary about James Dresnok, an American soldier who defected to the North after the Korean War and was married to her.
But there has never been an incident in which an American was abducted. (Although in recent years, Pyongyang has made something of a habit of detaining visiting Americans. Two people - University of Virginia student Otto Warmbier and Korean American missionary Kim Dong-chul - are currently being held.)
Now, Choi, of the abductees' association, said he was "50 to 70 percent" confident about the information he had from Pyongyang. Choi has a track record when it comes to finding out about abductees: He was the one who first heard about Kim Young-nam, a South Korean who was also kidnapped by the North and had been married to Megumi Yokota, a Japanese woman abducted as a schoolgirl.
But the State Department has not raised the case with the North Korean diplomats stationed at the United Nations, a senior administration official said. Nor has it asked the Swedish diplomats in Pyongyang, who represent American interests in North Korea, to take up the case there.
"There is no evidence that we've seen that indicates that he was abducted," the official said, although he conceded that there was no evidence that any of the Japanese had been abducted, either.
Indeed, experts said the case shouldn't be quickly dismissed. It was "certainly possible" that Sneddon had been taken, said Robert Boynton, author of "The Invitation-Only Zone: The True Story of North Korea's Abduction Project."
"Every time I find myself ruling it out, I realize that there is no more or no less evidence on Sneddon's disappearance than there was on the Japanese circa 1995," Boynton said. "It was all circumstantial."
Boynton, whose book focused on the Japanese abductees, cautioned against dismissing the idea because it didn't make sense.
"Why would anyone do this? Why would anyone go to such lengths to get something as simple as an English teacher? But North Korea has done this before," he said, with the Japanese abductees who worked as language teachers in Pyongyang.
Greg Scarlatoiu, executive director of the Committee for Human Rights in North Korea, said he was also inclined to believe that Sneddon was abducted.
Scarlatoiu noted the tense environment at the time. There was close cooperation between North Korea and nearby Burma - Pyongyang had reportedly been selling arms to the Burmese junta - and North Korean agents could have been operating in the area.
The U.S. House of Representatives had just passed the North Korean Human Rights Act, highlighting the nation's human rights abuses and offering assistance to anyone who escaped it. Plus, the biggest group of defectors to date - a group of 469 North Koreans - had just arrived in South Korea from Vietnam.
"The North Koreans were extraordinarily upset," Scarlatoiu said. "I wonder if our own U.S. government agencies could look into opening an investigation."