An art historian’s work is never done.

Gergely Barki, who works as a researcher at the Hungarian National Gallery in Budapest, was spending Christmas 2009 at home on the couch with his young daughter. They were watching Stuart Little when he noticed something odd about the painting hanging over the fictional family's mantelpiece—it bore a striking resemblance to a work by Hungarian artist Robert Bereny, which had last been seen in public in 1928.

Barki recognized the painting—“Sleeping Lady with Black Vase”—from a black-and-white photograph taken of the work during its last exhibition, in 1928. “It was not just on screen for one second but in several scenes of the film, so I knew I was not dreaming. It was a very happy moment,” said Barki. who had no idea how it ended up as set dressing in a 1999 children’s movie.

Barki, who is writing a biography of Bereny, went into full detective mode. “I started to write e-mails to everyone involved in the film,” he told the New York Post. He sent letters to the film’s creators, Sony Pictures and Columbia Pictures, finally receiving a reply from the film’s former set designer two years later.

According to Barki, the film assistant, whose name has not been reported, had picked up the painting in a Pasadena, Ca., antiques shop for just $500. Unaware of its origin or value, she used the work to decorate the apartment of the family—played by the disembodied voices of Michael J. Fox, Jonathan Lipnicki, Geena Davis, and Hugh Laurie—in the film based on E.B. White’s beloved book. When production wrapped, the assistant bought the painting from the studio and hung it in her apartment. “I had a chance to visit her and see the painting and tell her everything about the painter,” said Barki. “She was very surprised.”

Bereny was a member of the Hungarian avant-garde collective known as The Eight, who helped introduce Cubism and Expressionism to Hungary. While his work is highly regarded, Bereny is perhaps better known for his love affairs—he’s rumored to have dallied with actress Marlene Dietrich in Berlin in 1920 and—according to Barki—may have had a fling with Anastasia, the mysterious daughter of Russia’s last tsar, Nicholas II.

Thanks to Barki's good work and eagle eye, the painting has since been repatriated. The anonymous film assistant sold the painting to an art collector, who returned the painting to Hungary. It will be auctioned off by Budapest’s Virag Judit auction house on Dec. 13th, with a starting price of $110,000.