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I think it's stupid for them to say that everyone is "stumped."
If thieves can figure it out, then so can the "experts," or else they're not expert at all.
How would you like it if you were to go to the bank and they told you that some thieves found a way to take all the bank's assets, and your account is empty?
I would suppose it's likely that the thieves hang out and wait for a person to use their key fob to either lock their car or unlock it, and the thieves have a receiver that records the radio signal that the key fob puts out. Then they wait for the person to disappear, or to return later with the same car, and walk away, then the thieves playback the recorded key fob signal to unlock the car, etc.
When you use a remote device to lock OR to unlock your car, you are BROADCASTING a radio signal for all to hear, that is, for those with "ears" to hear.
So the way to prevent this problem would be, obviously, don't leave anything in the car worth stealing, but what about the car? If they can open the doors, they can tow the car away and steal it.
Especially young people like to lock their car as they're walking away from it, but maybe that's not such a good idea anymore. I'd suggest, you shouldn't use your key fob to LOCK your car, because someone might be hiding nearby recording your radio signal.
Another idea would be to have the push-button door locks at the door handle on the car, so that you have to key in a code by pushing those buttons, and stand close to the door when doing so, preventing anyone from watching you from the side at a distance.