When auction appraiser Josh Levine set out to catalog the estate of a local Arizona man moving to a retirement community, the last thing he expected to find was a multimillion dollar lost work of art.

"Interestingly, this estate first came to our attention when we were contacted to take a look at a signed 1992 L.A. Lakers poster," Levine, owner and CEO of J. Levine Auction & Appraisal, said in a statement. "We ended up signing a contract to auction the contents of the estate, and that's when we found many of the paintings stored away."

In addition to finding paintings by such artists as Kenneth Noland, Hazel Guggenheim McKinley, Jules Olitski and Cora Kelley Ward stored in the man's garage, Levine was shocked to discover what looked like an original Jackson Pollock buried under the stack. The splatters and swirls of the piece were emblematic of Pollock's celebrated work from 1936 until his death in 1954.

What followed over the next 18 months was an investigation of epic proportions (and tens of thousands of dollars) to verify that the painting was a true Pollock. During his research, Levine discovered that the garage was owned by the half-brother of a former New York socialite named Jenifer Gordon Cosgriff. In the 1950's, Cosgriff mingled in New York's elite art circles and built friendships with many of the artists discovered in the garage, including Pollock himself.

After she passed in the early '90s, Cosgriff bequeathed her art collection to her half-brother in Arizona. Until January 2016, they had been largely forgotten in storage.

After making the connection with Cosgriff, Levine examined the painting and hired a team of specialists to analyze the makeup of the paint. The team was able to accurately date the work to "the mid-twentieth century" with no pigments or binding media introduced in the late 1950s or 1960s detected.

"The forensic report really just reaffirmed what I already believed to be true based on the provenance," Levine said, adding that it's likely the work is one of the artist's missing gouaches. "I've spent hundreds of hours researching how this Pollock could end up here in Arizona, and I am confident that this is an original Pollock."

Despite some water damage and staining from secondhand smoke (a common problem in households from the mid-20th century), the June 20 auction for the piece is expected to fetch anywhere from $10 million to $15 million. The starting bid for the 22.5-inch by 32-inch piece is a cool $5 million.

So, what's in your garage?

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.