Last month, NASA’s inspector general, Paul K. Martin, determined that 517 moon rocks and other astromaterial samples that were lent between 1970 and 2010 had been lost or stolen. A report issued by Mr. Martin’s office found that 11 of the 59 researchers in the Houston and Washington areas who were audited could not account for all of the samples NASA had lent them, or the agency found other discrepancies, including researchers who had items that according to agency records either did not exist or had been lent to others. The space agency had also failed to update its records for 12 researchers who had died, retired or relocated, in some instances without returning the samples. One researcher, the report noted, still had lunar samples he had borrowed 35 years earlier though he never conducted research on them.

The report found that Johnson Space Center’s Astromaterials Acquisition and Curation Office in Houston, which maintains NASA’s collection of 163,000 astromaterial samples, lacked sufficient control over its loans of moon rocks and other items for research, education and public display. The samples that American and foreign dignitaries received as gifts were not included in the report, because the space agency does not track them. Moon-rock experts say NASA should keep an inventory of those as well, and they estimate that of nearly 400 moon rocks given to state and world leaders after the Apollo 11 and 17 missions, almost 200 have been lost, destroyed or stolen.

Spokesmen for NASA in Washington and Houston said the losses reported by the inspector general represented only a small fraction of the tens of thousands of astromaterial samples the space agency had lent to scientists around the world for more than 40 years. In particular, the lost samples from the moon amounted to less than one-hundredth of 1 percent of the samples that were safely returned in the past four decades.

“Although such losses at any time are regrettable, and NASA agrees with the I.G. report that continuing to improve certain procedures could reduce the rate at which they occur, the benefits to science of making these samples available for study have vastly outweighed the tiny risk of loss,” a NASA spokesman in Houston, William P. Jeffs, said in a statement.

NASA officials said they were implementing the recommendations in the report, which called for the space agency to require loan agreements for all types of materials and strengthen the inventory verification process, among other steps. Mr. Jeffs said that although several researchers involved in losing samples were reprimanded in letters from NASA, their research privileges were not revoked.

Few Americans have been as focused on moon rocks as Joseph R. Gutheinz Jr., a Texas lawyer who keeps a spinning globe on his desk reading, “Moon Rock Hunter.” The title is not official (the globe was a gift from one of his sons), but it might as well be: Mr. Gutheinz and his criminal justice students at the University of Phoenix and Alvin Community College in Alvin, Tex., have helped track down 77 moon rocks that were missing, including those presented to governors in Colorado, Missouri and West Virginia.

“If someone hands a governor a moon rock, and he keeps it or loses it, if you can’t protect something like that, maybe they’re not that vigilant,” said Mr. Gutheinz, a retired senior special agent in NASA’s inspector general office. “And if they’re not that careful, and they bring it home with them, what else have they brought home with them?”

Mr. Gutheinz was the undercover agent who led a Miami sting operation to recover a moon rock stolen in Honduras in 1998. It was called Operation Lunar Eclipse. Mr. Gutheinz ran an advertisement in USA Today reading, “Moon Rocks Wanted,” and a man called offering to sell him a real moon rock. The asking price was $5 million.