With the default English keyboard layout, the "action" key is adjacent to the "throw" key. A common result of this, is that a player fleeing infected will often mistakenly throw the weapon in his or her hands while attempting to open a door.
In the case of vehicles, this will result in immediate deletion of the gun from the server. I have unintentionally duplicated this on multiple iterations of .61.

On Tuesday, I had forgotten that I deleted my CFG file while attempting to fix another issue. This resulted in the loss of my FAL, which I had carried for weeks. A friend was nice enough to run and have a look at where I lost it, and saw this sitting up against the door against which I had errantly thrown my rifle. He was unable to interact with the rifle, and could no longer see it after re-logging in the same server.