A long-lost Hungarian masterpiece was hiding in plain sight all along—as a prop on the set of the Stuart Little movie.

"Sleeping Lady with Black Vase," a painting by Robert Bereny, disappeared in the 1920s. It remained missing until 2009, when Gergely Barki, an art historian at the National Gallery in Budapest, decided to watch Stuart Little with his daughter on Christmas.

"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," Barki told the New York Post.

He immediately began reaching out to Sony Pictures and Columbia Pictures. After two years of searching, he finally got in contact with the set designer, who told him she had the painting, which she purchased for $500, hanging on her wall.

"She had snapped it up for next-to-nothing in an antiques shop in Pasadena, California, thinking its avant-garde elegance was perfect for Stuart Little's living room," Barki said.

The set designer reportedly sold the painting to an art dealer, who returned it to Hungary. It's set for auction next month with a starting bid of $110,000.

Barki tells the Post the original buyer was probably Jewish and fled Hungary during World War II.

[Stuart Little screenshot via Vanity Fair]