How to unlock password protected iPhone
If you are faces with a password protected iPhone, you can still unlock and access iPhone favorites, address book, dial keypad, and voice mail. This trick is not a high tech technique, but just a simple unlocking steps to do. This simple steps can be done because iPhone has the security flaw. Gizmogo posted this steps like the followings:
Try to slide to unlock, tap emergency call, after that, double tap the home button.
Whoola, you will find yourself in iPhone favorites. From there, you could access other menu like address book, dial keypad, and voice mail.
If you are the owner and wants to avoid this security flaw, you could do the following.
1. In the iPhone home, go to Settings.
2. Click on General.
3. Click on Home Button.
4. Click on either “Home” or “iPod”.
By doing this, when someone is doing double tap, he/she will be redirected to the unlock screen (if you choose HOME).

Did not work on mine!