Melissa Lim remembers the first time she locked eyes with Noel Gallagher, the lead guitarist of Oasis. It was backstage at the Bottom of the Hill on Sept. 26, 1994, where the quarrelsome British rock band was making its San Francisco live debut in support of its platinum-selling first album, “Definitely Maybe.”

“He came over and sat down next to me,” she says. “I had never been backstage before, so I asked him, ‘Where’s the afterparty?’ And he goes, ‘What afterparty? Can I hang out with you tonight?’”

The encounter would play a major part in the group’s formative years, chronicled in the action-packed new documentary, “Supersonic” (from the makers of “Amy”), which hit U.S. theaters last month.

Three days later, after a disastrous concert at the Whisky a Go Go in Los Angeles — where the band members were high on crystal meth and saddled with mismatched set lists — things came to a head. Gallagher was struck in the face by a tambourine hurled by younger brother Liam, and decided he’d had enough.

Gallagher grabbed his passport, boarded a plane to San Francisco and reportedly went into hiding at Lim’s apartment in lower Nob Hill.

“He was very upset,” she says. “I took him in, fed him and tried to calm him down. He wanted to break up the band.”

As Oasis’ manager and record label staff frantically searched for him, Gallagher settled in with the San Francisco native.

“We went to Huntington Park to clear his mind,” Lim says. “We listened to music. We went record shopping.”

One day, while out for her usual supply of Snapple Strawberry Lemonade, Lim recalls bringing back a handful of British music magazines back to the apartment — all of them included prominent features on Oasis.

“San Francisco has a reputation of being a place where bands come to die, like the Band and the Sex Pistols,” says Lim. “I wasn’t going to let it happen on my watch. I told him, ‘You can’t leave the band — you’re on the verge of something big.’”

In “Supersonic,” without mentioning her specifically, the band’s producer Mark Coyle calls Lim a “spiritual animal” who took Gallagher under her wing and set him straight.

Gallagher’s memory of their time together is less clear, most likely impaired by his level of indulgence.

“If I close my eyes now, I can’t even picture the girl,” he says in the film. “I can’t remember her name.”

When The Chronicle asked Oasis to confirm Lim’s story, Gallagher declined to comment. But the memories are vivid for Lim, who still holds on to old photos of her and Gallagher during that pivotal period. She may not be named in the documentary, but Lim played a crucial role in Oasis lore.

Once Gallagher decided to resume his band duties, one of the first things he did was check into a studio in Austin, where he recorded the songs “Half the World Away” and “Talk Tonight”:

“All your dreams are made,

Of strawberry lemonade,

And you make sure I eat today,

You take me walking,

To where you played when you were young.”

On the chorus, Gallagher sings, “I want to talk tonight/ Until the mornin’ light/ ’Bout how you saved my life.”

Lim says she and Gallagher stayed in touch as the tour continued, meeting when Oasis shot the video for the song “Supersonic” at the Cabazon Dinosaurs in Southern California. They would also talk on the phone regularly, with Lim answering the phone with a line from the film “Bye Bye Birdie”: “What’s the story, morning glory?”

She often had to console him as the brothers fought nonstop with each other and just about anyone else who entered their orbit, including bandmates, relatives and associates.

Lim’s long-distance relationship ended when Gallagher met his future wife, Meg Matthews, at the tail end of 1994 (they married in 1997, divorced in 2001).

When Oasis returned to San Francisco to perform at the Fillmore in early 1995, Lim found Gallagher to be distant. But hoping to maintain their relationship, she told him, “It’s OK, I won’t look back in anger. I know we’re just friends.”

Although Gallagher didn’t tell her at the time, Oasis’ second album was titled “(What’s the Story) Morning Glory?” It sold more than 22 million copies worldwide, launched the career-defining singles “Wonderwall” and “Don’t Look Back in Anger,” and led to the 1996 concerts in Knebworth, England, which drew 250,000 fans over two nights.

The documentary closes with that crowning moment, even though Oasis pressed on to diminishing returns until 2009.

Watching “Supersonic,” Lim says she wasn’t disappointed by Gallagher’s callous attitude about their time together.

“Keith Richards can remember the name of his milkman from when he was 8 years old,” she says. “I don’t know what’s going on with Noel, and that’s fine. I was a part of something that touched so many people. That’s good enough.”

Aidin Vaziri is The San Francisco Chronicle’s pop music critic. E-mail: avaziri@sfchronicle.com Twitter: @MusicSF

Supersonic: Documentary. Starring Noel Gallagher, Paul Arthurs, Christine Biller and Mark Coyle. Directed by Mat Whitecross. (R. 122 minutes.)

To see a trailer: https://youtu.be/9waBd3yPOLE