since they did know how to open it, get in, start the engine and leave in few seconds.

I think you may be attributing more organization and skill to the thieves than is warranted.

If I wanted to steal your car under the circumstances described, I would first disable the alarm. If what Lupo said earlier is correct, a screwdriver blade with a T-handle on it would do it just as quickly as a key.

Then I would slide a floor jack under the transaxle, raise the front end 8" off the ground and slide a dolly wheel set under each front wheel. This would take about 15 seconds with two people working at it.

I would then back my getaway vehicle (it wouldn't have to be any bigger than your Golf) up to the dolly wheels, and being a clever thief I would have prepared a method whereby I could secure the dolly wheels to my getaway vehicle with a couple of chains or maybe a cable and come-along system, and drive away. This would take another 30 seconds or so.

In less than a minute's time, I could make your car disappear with no alarms, no loud noises, and no activities that would look unduly suspicious to a bystander.

tanstaafl.