Don't feel bad. I once went to the range to shoot my S&W 642. After shooting I cleaned the gun and reholstered it (mika pocket holster) without reloading. On my way out the door the next morning for a quick run to the store I grabbed it off the shelf and stuck it in my cargo shorts pocket. It was three days later that I pulled it out of the holster to check for lint and

NO AMMO!!! That will never happen again

Always inspect the weapon each time you pick it up.