Written by Nancy Coleman, CNN

The story sounds like something out of a film noir brought to life. It has every element of a good mystery: a socialite who spent her days mingling with New York's best and brightest, a lost painting found years later in an unexpected place, and -- perhaps most notably -- a potential $15 million price tag.

So when a rare Jackson Pollock painting was found in an Arizona garage, figuring out its origins wasn't just about analyzing brush strokes. Like any good mystery, uncovering the painting's history took tracking down the people behind it.

'God, that looks like a Jackson Pollock'

The mystery began with a signed L.A. Lakers poster. When a Scottsdale, Arizona, man was headed to a retirement home, a neighbor helping with the move found the collectible in the garage and suggested contacting an auctioneer to appraise it.

Josh Levine, owner of the auction house who was called to look at the poster, estimated the signed Lakers memorabilia would be worth about $300. But when they went to the man's garage, what they found could be 50,000 times more valuable.

A collection of several modern paintings were among the man's belongings -- one of which featured an amalgamation of splatters and swirls similar to Pollock's contemporary style. "As we're going through the stack and we're down to this last piece ... I was like, 'God, that looks like a Jackson Pollock," Levine told CNN.

The paintings seemed out of place. In a region where most homes are filled with traditional southwest art, the eccentric shapes and abstract details were "really weird," Levine said. Levine brought the artwork back to his office, where it sat for three months. He struggled to find the link between a man from Nebraska and his little collection of modern New York art.

The socialite connection

An early photograph of Jenifer Gordon Cosgriff. Credit: Susan Kern-Fleischer

When Levine contacted the owner's attorney, he bridged the gap between the Arizona garage and New York's modern art scene: a half-sister, Jenifer Gordon Cosgriff.

Gordon Cosgriff, a New York socialite, was considered the "black sheep" of the family, Levine said. While the rest of the family stuck to the Midwest, Gordon Cosgriff spent her time rubbing shoulders in the 1950s with elite members of the art community on the east coast. She ran in the same social circles as notable art critic Clement Greenberg, modern artist Hazel Guggenheim McKinley ... and Jackson Pollock.

Learning about Gordon Cosgriff's history and relationships was a turning point in Levine's research. The piece that had first seemed reminiscent of Pollock's work now had a plausible connection to the artist himself. When Gordon Cosgriff died in the '90s, her brother packed up her belongings -- including her art collection -- and put them in his garage, where they would remain until January 2016.

The costly authentication

Artist Hazel Guggenheim McKinley, left, and Jenifer Gordon Cosgriff at an art gallery. Credit: Susan Kern-Fleischer

But it would take more to prove the painting's origins than a personal connection between Gordon Cosgriff and Pollock.

For nearly 18 months after unearthing the painting, Levine spent tens of thousands of dollars trying to authenticate the piece. He fell down a rabbit hole of research into Gordon Cosgriff's life, poring over her letters and hiring a private investigator to help. His ultimate goal: to track Gordon Cosgriff's location down to a Pollock showing where she reasonably could have acquired the painting in question.

Once he confirmed her attendance at his showings, Levine brought forensics experts into the mix to analyze the painting itself. "All I was interested in was, was it executed before Jackson Pollock was dead, before 1956?" Levine said.

After examining the kind of paint used, the forensics report confirmed what Levine had hoped: The painting was likely one of Pollock's missing gouaches, a specific style of painting using water and a binding agent, from around 1945 to 1949. "I actually felt weightless," Levine said. "I was actually kind of worried I was having a panic attack or something."

Restoration for a new home

Auctioneer Josh Levine poses with the untitled Jackson Pollock painting. Credit: Susan Kern-Fleischer

The painting is heavily damaged and needs to be restored, Levine said. The darker, cream-colored swirls throughout the canvas would have originally been a brighter white. Levine said the damage comes from the artwork spending years in a house with heavy smokers, which was not unusual for the mid-20th century when it would have resided in Gordon Cosgriff's home.

Restoration, a process that involves cleaning the painting by hand over a couple of weeks, could cost up to $50,000. Despite the damage, Levine's rabbit hole is expected to pay off. After remaining out of the public eye for years, the untitled Pollock piece will be auctioned off on June 20.

Bidding starts at $5 million, but Levine expects the final price tag to be anywhere from $10 million to $15 million -- far surpassing the estimated $300 value of the signed Lakers poster.