If you wanted to compare both versions of Vincent van Gogh’s Portrait of Dr. Gachet in person, you couldn’t. While the second one currently hangs in Paris’s Musée d'Orsay, the public hasn’t seen the original painting since 1990. In fact, nobody’s really sure where it is—after its owner Ryoei Saito died in 1996, the precious item passed from private collector to private collector, but the identity of its current owner is shrouded in mystery.

As Smithsonian Magazine reports, Portrait of Dr. Gachet (1890) is one of a dozen paintings in “Missing Masterpieces,” a digital exhibit of some of the world’s most famous lost artworks. It’s not the only Van Gogh in the collection. His 1884 painting The Parsonage Garden at Nuenen in Spring was snatched from the Netherlands’ Singer Laren museum earlier this year; and his 1888 painting The Painter on His Way to Work has been missing since World War II. Other works include View of Auvers-sur-Oise by Paul Cézanne, William Blake’s Last Judgement, and two bridge paintings by Claude Monet.

Paul Cézanne's View of Auvers-sur-Oise was stolen from the University of Oxford's art museum on New Year's Eve in 1999.Ashmolean Museum, Wikimedia Commons // Public Domain

The new online exhibit is a collaboration between Samsung and art crime expert Noah Charney, who founded The Association for Research into Crimes Against Art. It isn’t just a page where art enthusiasts can explore the stories behind the missing works—it’s also a way to encourage people to come forward with information that could lead to the recovery of the works themselves.

“From contradictory media reports to speculation in Reddit feeds—the clues are out there, but the volume of information can be overwhelming,” Charney said in a press release. “This is where technology and social media can help by bringing people together to assist the search. It’s not unheard of for an innocuous tip posted online to be the key that unlocks a case.”

The exhibition will be online through February 10, 2021, and citizen sleuths can email their tips to missingmasterpieces@artcrimeresearch.org.

[h/t Smithsonian Magazine]