My Car is super highly Secured

I've been to a friend of mine yesterday and sadly i forgot the keys inside the car and locked the doors. Usually in these situations I have to go back home and get my spare keys. But this time it was different. One of my friends said "wait I have a master key that opens all cars!" . I was like "hahaha ok that's a joke, so what are we going to do now". And then I was surprised that he actually was trying to open MY CAR with HIS car's keys !!! . The strangest was that it opened!! .. If I didn't see this myself I would have thought that it's a trick. My car is a hyundai and his is a slavuta!!. And it seems that he's tried this before on different cars .. Although my car is old .. but not that old!! I think I'm gonna have to use my new security alarm system on that car. But after I fix it because it got hit in an accident on the very same day! :D