Germany's Spiegel newspaper reported earlier this week that the 20GB hard drive contained a raft of information about Brandenburg police, including details of political security situations.
Industry analysts claim the blunder was inevitable.
"Even when companies or individuals believe they have wiped the hard drive clean, it is blatantly clear how easy it is to retrieve sensitive information from them both during their current lifetime and beyond it," said Peter Larsson, CEO of mobile technology company Pointsec.
"This week's exposure of leaked and highly critical information from the Brandenburg police in Germany reinforces how important it is to never let mobile devices or hard drives leave the office without being adequately protected with encryption and strong password protection - even after they have been discarded," Larsson continued.
The drive was eventually bought by a student from Potsdam who alerted police once he realised what it contained. German Minister for the Interior Jorg Schonbohm has initiated an investigation into the sequence of events that led to it appearing on the auction website.
In February SC reported organisations are putting themselves at risk by not properly destroying data on hard drives. Research by the University of Glamorgan revealed that valuable or embarrassing information is easy to find on computers that had not had files erased properly.