"We were packing everything up, having a coffee in his house with a crew and I was just like 'Where are all your medals?' And he says 'Oh I keep them in my basement.' And I was like 'What here?'"
Downstairs was a haphazard treasure trove of memorabilia. Scheduled to fly home the next day, the 39-year-old British director begged Johnson to let him film it.
The resulting footage is some of the most memorable of Gordon's documentary "9.79*."
Johnson, now 51, holds up a battered cardboard box full of medals and pulls out his bronze from the 1984 Olympics. Diving in again, he produces the twisted ribbon that goes with it.
Gordon's film is about the infamous 1988 100-metre final in Seoul, the storylines that led up to it and the men who took part. The 80-minute film debuted on the weekend at the Toronto International Film Festival.
While Gordon acknowledges "9.79*" does not shed new light on the well-documented race, it is a polished, beautifully shot look at the Olympic final and its colourful characters _ from the eight sprinters themselves to the surrounding cast of coaches and doping experts.
The film starts with the pre-race commentary over a look at the empty starting blocks in that supersized Seoul stadium before delving into the stories of Johnson and rivals Carl Lewis, Linford Christie, Dennis Mitchell, Robson Da Silva, Calvin Smith, Ray Stewart and Canadian Desai Williams.
Of the eight, only Smith and Da Silva have never been linked in some way to drugs. Lewis once showed minor amounts of stimulant, a finding Gordon says would not result in a positive test today. Lewis was not sanctioned after reportedly explaining away the tests.
Gordon said the idea for the Johnson project came during a 2008 visit to South Korea when he was promoting one of his three documentaries on North Korea (which focus respectively on Korea's 1966 soccer team, two young gymnasts, and the last American defector living in the country).
During such visits, he was always asked when he was going to do a movie on South Korea. His stock answer was that he didn't have a story in mind. But on this visit, he cast his mind back to the Seoul sprint final.
He was 15 at the time of the race.
"For me it was the greatest race ever — four men under 10 seconds. That never happened before. It was a real breakthrough moment for sprinting."
He did some quick research on the spot, with the idea of pitching it to the BBC upon his return.
"Then I just realized there is one heck of a story here — on all eight. It's not just about four men going under 10 seconds. That's kind of the hook, but the real story is all eight of them ... Also I felt it's not about drugs either. It's about what hurdles they all overcame."
Smith came from a poor, rural Alabama background to become the fastest man in the world. Lewis' parents were involved in the civil rights movement and eventually left the South for a better life.
Their son become a fast-running, fast-talking sprinter who proved to be the perfect foil for the taciturn, single-minded Johnson who once said famously "Gun go, race over."
Johnson, Williams and Christie all left Caribbean countries for vastly different new homes. Da Silva grew up in a Brazilian slum and says his first race was to escape the police.
"What they all came to to be at that start line, I thought there was an incredible depth of a story," Gordon said in an interview. "And then what's happened to them since, because they've all gone different paths. They're not all involved in track, they've not all had easy lives afterwards. I thought it was fascinating."
Johnson comes across as a fallen icon, one of many dirty sprinters who paid the biggest price for being caught winning on track's biggest stage.
Some things never change, it seems. Almost 25 years on from Seoul, Gordon's film rolls out as the doping spotlight focuses on a reluctant Lance Armstrong.
A former assistant producer at Sky TV, Gordon formed his own production company VeryMuchSo in 2001. Other recent films include a BBC documentary on British cycling star Victoria Pendleton and "Match 64," a FIFA film on the 2010 World Cup final.
He pitched "9.79*" to the BBC, which eventually said yes although it took almost two years to get the proper budget in place. ESPN became involved much later in the process.
The BBC plans to show a shorter version of the movie. The full version will be aired on ESPN on Oct. 9 as part of its acclaimed "30 for 30" documentary series.
The decision to have its premiere at TIFF was determined by timing rather than the link to Johnson.
"Very fortunate ... For me it's a great piece of timing," said Gordon, who did not finish the final edit until Sept. 1.
It was never a rush job, Gordon hastens to add. He just wanted to spend as much time as possible on it. Not to mention his editor was unavailable during the Olympics, having hired his house out to an American equestrian.
Gordon's goal was to get all eight sprinters in his film.
"They all have their own version of the truth," he said. "And actually it may be the truth in their eyes."
Of the eight, Christie proved to be the most difficult to get on board.
One person he could not get on camera was Andre Jackson, the American accused of spiking Johnson's drink to make him test positive.
"The mystery remains," mused Gordon.
Johnson agreed after meeting Gordon in July 2010 in Toronto. He was open to the idea but "it took quite a bit of explaining," the director said.
"I was like 'I'll show you my films and you decide what sort of job I do,'" said Gordon, who prides himself on being non-judgmental in his work.
Gordon returned in January 2011 to film Johnson, something the BBC wanted to see before they committed to the project. There was a subsequent visit in January 2012.
For Gordon, who serves as both producer and director, "9.79*" is a special project because of the satisfaction overcoming the obstacles he had in getting it made.
And while he spent long stretches away from his wife and two young daughters, the movie-making journey with his three- or four-person crew had more than its share of moments.
"I really enjoyed the characters that you meet and the stories they've got to tell over and beyond what is part of the story," he said.