I'll be honest and say I don't know a tremendous amount about key cloning but my understanding is that it's far less common than relay theft. Both techniques are feasible ways to steal a keyless entry and keyless ignition car, but with relay thefts, thieves use relay devices to amplify the signal from the key fob in your home to a transmitter near your car, which essentially tricks your car into thinking the key is present. This allows them entry into the car, where they can use the start-stop button to start the car without the key. However, key cloning is far more sophisticated, requiring precision and devices to steal the key fob code as it generates it to unlock the vehicle.

I would continue to use a faraday bag or tin box as long as you're sure it's working. If you're very concerned, you can look in the car's manual to see if you can actually deactivate keyless ignition - if not, you can ask your local dealer if it's possible to deactivate it. Aftermarket immobilisers or trackers might also be worth researching. CCTV, or a Ring Video Doorbell, is also an option: amzn.to/3j8r25X