Really? It’s invisible in the machine, but otherwise I always have my eyes on my stuff. All you have to do is shout if you see someone rummaging. Once I even expressed concern for my wallet, and they took it and put it aside while they wanded me.
The sort of set-up I have used consists of the x-ray machine with the walk-through metal detector to the side of it. You put your things on the conveyor belt and then have to walk through the metal detector. Sometimes there are a couple of people in front of you also going through. In that time your bag as gone through the machine and is waiting on the other side. It is screened from you by the machine and , as I said, it can be out of your sight for a good minute or so.
Especially if your Dopername is your real name. But thats not the case right? 
All you have to count on is not running into the rightful owner of the suitcase – AND having him/her recognize it ; otherwise walking through an airport with a suitcase in your hand is completely unremarkable.