Former U.S. president Bill Clinton's Arkansas files were hiding a piece of missing Apollo 11 moon rock. (Associated Press)An archivist sifting through the papers and memorabilia amassed during former U.S. president Bill Clinton's time as Arkansas governor found a moon rock brought back by the Apollo 17 mission that had mysteriously gone missing.

The rock, which weighs less than half an ounce, was found in one of the roughly 2,000 boxes of Clinton materials that are housed in Little Rock, said Bobby Roberts, who directs the Central Arkansas Library System.

"This morning, one of the processors opened up a box and there's the moon rock, out of nowhere," Roberts said this week.

The rock was collected during the 1972 Apollo 17 mission and was given to the state more than 30 years ago.

The Arkansas Democrat-Gazette first reported the rock was missing last year. Since then, Roberts said he has been following the news about the moon rock.

"It kind of became Arkansas' mystery about 'Where's the moon rock?'," he told The Associated Press.

Roberts said he's not sure how the rock ended up among paperwork from when Clinton served as governor, but he said he's glad it has been recovered.

"It really is something from an important era in the history of the country and you hate to see it disappear," he said. "I guess it's one more Arkansas mystery solved."

An Arkansas museum employee discovered another moon rock last summer, according to the Democrat-Gazette. That piece of the moon was from the Apollo 11 mission in 1969.