If the ignition switch is disabled the jumper wont do anything. I worked in Auto Theft for many years. Car theives are in and out.
They dont search cars for kill switches. That just doesnt happen..... Most of the time it will be at night and finding a kill switch at night is nearly impossible!
I would interview every car thief I arrested (Not as evidence, just to educate myself cause most were juvi's and we cant interogate them but we can talk to them) and I would also ask how many times they got into a car and it simply wouldnt start and they would say almost never. I asked what happens if it doesnt start? Do u search the car for kill switches? Their answer? "Nah, we bounce".
Remember, most car theives are NOT professionals they are juvi's.... Yep, they can learn really quick but they aint rocket scientists and aint pulling the dash apart looking for kill switches that just doent happen.