Short of someone outright giving the child the gun, that’s the only option left. If a 9 year old can get to a gun, it’s improperly stored no matter where it is.
The statistical probability of this happening is probably not zero, however, it is still probably remote in the extreme. Even if it were to happen, however, as someone else pointed out: that would still be considered improper storage, because the point is that nobody but a responsible adult should be able to get to it, especially not children. 
If that’s the case probably not charge. I’m sure that’s happened at some point. But kids are playing with guns that are just left out in a lot of these cases and for those, yeah, maybe someone should face charges.
Short of someone outright giving the child the gun, that’s the only option left. If a 9 year old can get to a gun, it’s improperly stored no matter where it is.
That’s true but in these cases has the gun actually ever been properly stored in a locked safe and the kid nicked the key or something?
The statistical probability of this happening is probably not zero, however, it is still probably remote in the extreme. Even if it were to happen, however, as someone else pointed out: that would still be considered improper storage, because the point is that nobody but a responsible adult should be able to get to it, especially not children. 
If that’s the case probably not charge. I’m sure that’s happened at some point. But kids are playing with guns that are just left out in a lot of these cases and for those, yeah, maybe someone should face charges.
Yep mistakes happen of course but most if not all of the time it’s just neglect.