Well
I have never heard of this happening. If they check out your bag between the check in desk and the plane, they do the standard checks and put it back. If for some reason they didn't like something about it, for example the electronic grip was switched on or the hopper light was on they would pull the bag and get you of the plane to check it over. I am not sure they search the bags if your not present I think they just scan them.
As I said I have never heard of this happening it is the custom guys job to now what this stuff is. They have never seemed fazed by any of our markers or air systems. Just make sure no batteries are connected or electronics live and the air bottle is empty and open.
No problemo
Alan..............