This happens when every officer assumes the previous officer did a thorough search before hand. There was a case where a Colombian gang member killed himself in a interrogation room with a gun he had on him. In the video you can tell the officers were both upset by the fact he got a gun through security and the fact they knew they will all be fired.
I was always trained to run my thumbs down either side of the spine. That would’ve found it. Someone’s getting sloppy.
CC