This blue thing is a closing part of a cheap pen, it fitted well. The method was very similar as in the video in my first post about problem - I just inserted it, my friend was holding a laptop and I just spinned it and pushed like hell. Unfortunately I've broke the lock, because I am unable to insert the key (in case if I find it :P) because this mechanism is blocking this little hole on right.
So.. if you lose your key, use pens around the house and open it :D
Edit: I decided to post full sized photo, because it's (in my opinion) masterpiece of security photoart ;) HERE