So how widespread of a problem is this?
Our media partner, the Mercury News, did an in-depth report on it and found 944 guns were lost since 2010 -- many were stolen.
The guns were stolen from behind car seats and glove boxes, gym bags, dressers and under beds.
Officers have also left their weapons behind on tailgates of vehicles, car roofs and even on a toiler paper dispenser in a car dealership's bathroom.
Of course, the worse case scenario is when one of these weapons is used in a crime, like in the Steinle case.
The former police chief of Piedmont had a gun stolen from his car and it ended up being used in a shooting in San Francisco just a few months later.
So which department saw the most stolen weapons?
The CHP had the most, with a total of 40 taken since 2010, followed by the Department of Fish and Wildlife, the DEA, San Francisco Police Department, Alameda County Sheriff's Office and the Oakland Police Department.
Some of the departments, like the Alameda County Sheriff's Office and the San Francisco Police Department, now prohibit officers from keeping their guns in their vehicles overnight.