The Federal Bureau of Investigation was unable to obtain any of Democratic presidential nominee Hillary Clinton’s mobile devices while she was the top U.S. diplomat, but now we sort of have an idea why.

The FBI was unable to obtain any of the Blackberry mobile devices Clinton used while heading the Department of State, according to newly-released documents summarizing the investigation into Clinton’s handling of classified emails.

Clinton had 13 mobile devices that she potentially used to access emails on her private clintonemail.com server based out of her Chappaqua, New York home. At least eight of these mobile devices were used while she was secretary of state, but Clinton’s lawyers were unable to find any of them.Clinton aides told FBI investigators the former diplomat went through phones often, and the “whereabout” of her old phones would become unknown once she switched to a new device.