In the late nineties/early aughts, I worked for a company that hired a pair of guys after those guys showed up holding basically all the data from one of the company's services. The company started using these guys' custom software instead.

The server running this software was in our main server room although it was technically not our department. So one day, when a fairly serious bug was found, I had to chaperone the non-technical person into the service room. She was on the phone with these guys. For political reasons within the company, all I could do was watch. They instructed her, over the phone, symbol-and-letter by symbol-and-letter to add to live production code. What they added? A giant "if false" block around the buggy code.

True. Then again, I've heard of many better hiring practices as well.

Even odds it's a current employee, anyway.