Most likely kicked/moved by police, they didn't know if he was dead.
Though with columbine, they did check E&D for explosives.
Usually they try not to disturb a crime scene, but they could have logged that they kicked the gun.
_________________
And everything I hoped for has been strangely set aside.
Reason for living,
My mind is forgiving.
And destiny is proving to be absent from my life.