the invention is a system for retrieving loose metallic debris , such as stray radioactive marker bullets , from a borehole in a subterranean formation . the system can be used to retrieve stray radioactive marker bullets during placement of the radioactive marker bullets in the subterranean formation . the system utilizes a downhole fishing tool having at least one recessed magnetic surface for attracting and holding stray radioactive marker bullets . the recessed magnetic surface allows the fishing tool to be removed from the borehole without scraping off retrieved marker bullets that are held against the magnetic surface .