Shirkers is about a kidnapping. A strange kidnapping. One in which the precious cargo held hostage isn’t a person, but a film.

The Sundance award-winning documentary tells the story of Los Angeles-based, Singapore-born film-maker Sandi Tan, whose first feature, made when she was still a teenager, was stolen before it could be completed. Twenty years later, when she was miraculously reunited with the unseen footage, Tan decided to return to Singapore and revisit the making – and losing – of the film that haunted her for decades.

The resulting documentary is a collage of interviews with the people who worked on the project, footage from the original film, and letters, drawings and photos from Tan’s youth. It’s an annotated love letter to the people and places she left behind. After it premiered at Sundance in January, the New Yorker described it as “an exemplary work of counter-lives and alternative histories, intimate self-portraiture and cultural reconstruction, hard-won empathy and painful reconciliation”.

I don’t think of Cardona as a villain at all… but it was important he not hijack the film a second time Sandi Tan

Born in Singapore in 1972, Tan was a teenage cinephile who spent her free time devouring movies. She describes her younger self as “lonesome” and “offbeat”, hungry to connect but “relentless”. At 14, she started writing under a pseudonym for culture magazine BigO; at 18 she became the film critic for the Straits Times, Singapore’s biggest national newspaper. During this time she also took an evening class in film production taught by an American named Georges Cardona, who would go on to become her mentor.

“I was this 19-year-old with interests that no one else had, and in walks this person who loves the kinds of movies that I wanted to know more about, and learn to make,” Tan says of Cardona, when we meet on a stuffy, grey summer afternoon at this year’s Sheffield Doc/Fest. “We talked the same language,” she says. “I thought in some ways he was a teenage girl [and] would be my best friend.”

The older, more experienced Cardona charmed Tan with fanciful claims about his Hollywood connections, maintaining, among other things, that he was the inspiration behind James Spader’s character in Steven Soderbergh’s 1989 film Sex, Lies and Videotape. So, when Tan and her friends decided to make a film, it made sense that Cardona would shoot and direct her script. He encouraged Tan and classmates Jasmine Ng and Sophie Siddique to pool their savings and invest them in the film’s production. Despite the fact that he was twice their age and married with a young child, the four became close friends. Together, they made Tan’s movie. Filmed in 1992, the original Shirkers was an indie road movie starring Tan as a 16-year-old serial killer named “S”. Ng and Siddique edited and produced the film respectively. But that summer, without warning, Cardona vanished, taking 70 cans of 16mm film with him.

A scene from Shirkers. Photograph: Shirkers extra film stills

It was an act of betrayal that left Tan devastated. She left Singapore to study in the UK and then the US, and lost touch with her friends. She pursued film-making at New York University, making short films that travelled as far as the short film festival Clermont-Ferrand in France, where her 2001 Gourmet Baby played in competition. But making another feature seemed, at that point, impossible. Moving to LA, she instead began work on a novel, The Black Isle. Published in 2012, it is a hefty, gothic ghost story, set over a 60 year-period. Critics lapped it up; Vogue called it “gulpable”.

Then, out of the blue, as the press tour for The Black Isle was beginning, she received an email from Cardona’s widow, 10 years after his death. She had the Shirkers reels. Did Tan want them back?

“I was like, oh my God, I’ve been searching for 20 years for this!” she says. “These things started arriving at my house and we began corresponding.” For the following three years the film – all 70 cans of it – sat in Tan’s house in boxes until she was able to find the courage, and the money, to get the reels digitised. Once she saw the footage, it was as though a portal opened to a life she’d forgotten. She decided to use the footage to make something new: “This film is an enormous, overdue ruse to get my friends back together again, and to talk about this thing that I couldn’t talk about for a long time.”

Both in person and in the film, Tan reveals herself as a born storyteller, prone to tangents but attuned to details. She’s clever and self-deprecating – so much so that initially she didn’t want to appear in her documentary at all. It was her friend and colleague Enat Sidi (who worked as an editor on The Wolfpack and the forthcoming XY Chelsea) who made her realise she had to. “She came to my house and saw my archives – my letters, and my VHS tapes, and old issues of the zine Exploding Cat, and she looked at me like, ‘Sandi, this movie is about you.’”

Sandi Tan photographed at this year’s Sheffield Doc/Fest for Observer New Review. Photograph: Fabio De Paola/The Observer

How did Tan find looking at the lost footage? Was it traumatising? “It was different,” Tan says. “I was much stronger. I was weaponised with storytelling.” In other words, her success as a novelist meant she could tell her story on her own terms. “I had a new group of people, and an agency. I didn’t feel any anger anymore.”

Instead, the feeling was more like closure. “I was watching Twin Peaks: The Return, which takes place 25 years after Fire Walk With Me – one of my favourite movies of all time,” she says. “1992 – fire walk with me. 2017 – the return.” It was an a-ha! moment. “The timeline was the same [as with my films]. I felt like I was Laura Palmer coming back to solve my murder all over again, which is what I’m essentially doing in the film. I’m solving this black hole my life had fallen into.”

Yet anger would have been an understandable emotion. Though the film is largely ambivalent about Cardona, he comes across as a creep; a creative leech who manipulated the girls and used their money to complete the project before commandeering it himself.

Tan sees it differently. “I don’t think of him as a villain at all. He was a very strange friend. I mean, he didn’t produce anything. He never finished anything, ever,” she says, expressing pity for a man so desperate to make good on his tall tales that he stole a film from three 19 year-old girls. Still, she was adamant he should not become Shirkers’ centre. “It was important he not hijack the film a second time.”

Looking at the original footage now, with its plié-ing ballerinas, smiling toothbrush salesman and popping, pastel colours, Shirkers’ oddball universe feels uncannily familiar, sharing cinematic DNA with films that came later, such as Wes Anderson’s Rushmore, David Lynch’s The Straight Story and Terry Zwigoff’s Ghost World. Spooky, when you consider that in 1992 none of them had been made.

Tan says that when she first saw those films, she recognised her own, and felt that the original Shirkers was sending her “distress signals” via these other movies. “The film was always alive,” she insists. “These cans of film were sending out radioactive pulses. Lawrence Everson, the sound designer, and I talked about the film being a living organism that was like a kidnapped person – Georges kept it in a room in his house, as if it were a human.”

Tan is less interested in discussing the film’s critical reception (very good, actually) than she is in the kids attending its screenings. “I get these kids pledging allegiance to the Shirkers army. At the True/False film festival, all these weeping kids would come up to me after the screening. They weren’t living in cultural centres like LA or New York, and so they were excited to see a film that showed kids living in the middle of nowhere doing something impossible. Teenagers of all ages are moved by this – teenagers who are in their 50s and 60s with unfinished projects are telling me that now they’re going to finish something.”

“When I was 18, I had the idea that you found freedom by building worlds inside your head,” her voiceover declares in the film’s opening scene. It’s this teenage sense of obsession and boundless imagination that makes Shirkers so transportive. Tan calls it “mania”. “I had to relive what it was like to have your head spinning all the time, unable to sleep because you had all these ideas you couldn’t begin to fulfil because you were a teenager,” she deadpans. “I’m a very method filmmaker.”

Shirkers is on Netflix from Friday