Q: stolen iphone

What to do if your iOS device is lost or stolen

http://support.apple.com/kb/HT5668

If it was locked with the standard four-digit passcode, it's not impossible to crack, but unless the thief would have some reason to believe you had very valuable information on the phone, it's unlikely that they'll bother. It's probably that your iPhone has already been restored, erasing all the data on it. You should, however, change passwords to any online services - iTunes Store, bank accounts, etc. - you had stored on the iPhone, just a precaution.

Regards.