Human Interest 'Stolen' Charles Darwin Notebooks 'Worth Millions' Returned to Library With Mysterious Note 20 Years Later One of the notebooks contains the "Tree of Life" sketch drawn by Charles Darwin in 1837 By Jason Hahn Jason Hahn Jason Hahn is a former Human Interest and Sports Reporter for PEOPLE. He started at PEOPLE's Los Angeles Bureau as a writer and reporter in 2017 and interviewed the likes of Kobe Bryant, Arnold Schwarzenegger and Tom Brady. He has a B.A. in English from the University of California, Berkeley, and a Master's degree in Journalism from Columbia University. He previously worked for Complex Magazine in New York City. People Editorial Guidelines Published on April 5, 2022 03:30PM EDT Photo: STUART ROBERTS/University of Cambridge/AFP via Getty Notebooks belonging to Charles Darwin — the English naturalist known for proposing the theory of evolution — were mysteriously returned to Cambridge University after they were likely stolen more than 20 years ago, the British institution said. The notebooks were left in a pink gift bag placed outside of librarian Jessica Gardner's office on March 9, according to a post on the university's website. It was the first time any Cambridge staff members had seen the two items since they were alerted to their disappearance during a routine check in January 2001. Initially, the university believed the notebooks were misplaced in one of their storerooms — which contain around 10 million books, maps and manuscripts — after they were photographed in late September 2000. But when the items weren't recovered in the years that followed, Gardner organized an extensive search involving a team of specialist staff members in 2020. The team came up empty-handed, leading experts in cultural heritage theft to say the notebooks had likely been stolen, according to the post. Russian Security Guard Doodles Eyes on $1M Painting During His First Day on the Job STUART ROBERTS/University of Cambridge/AFP via Getty "My sense of relief at the notebooks' safe return is profound and almost impossible to adequately express," Gardner said in a statement. "They may be tiny, just the size of postcards, but the notebooks' impact on the history of science, and their importance to our world-class collections here, cannot be overstated," she added. Gardner said the notebooks appeared to have no obvious signs of damage and were wrapped in plastic. Couple Mistakenly Defaces $400,000 Artwork in South Korea Gallery "I am incredibly glad to hear of the notebooks' safe return to their rightful home, alongside the rest of the University Library's remarkable Darwin Archives," Stephen J. Toope, Vice-Chancellor of Cambridge University, said in the statement. "Objects such as these are crucial for our understanding of not only the history of science but the history of humankind," he continued. "I'm delighted to learn that the notebooks will be going on public display this summer, giving visitors a once-in-a-lifetime chance to come face-to-face with Darwin's Tree of Life sketch." RELATED VIDEO: Woman Gifts Portrait of Grandfather After he Recovers from Covid-19 In a 2020 BBC article about the notebooks, the outlet estimated the rare items could be "worth millions." The university still does not know where the notebooks have been since their disappearance, and the person who returned them did not reveal their identity. But they did leave a message for Gardner, which simply read: "Librarian, Happy Easter, X."