What to do when iPhone got stolen?

Okay, so I lost my iPhone 4s last night and it appeared as offline immediately upon signing on to Find My iPhone. I placed it on Lost Mode right away. I got an email that my Apple ID password got changed (i was able to change it again though). I'm thinking that the thief used my phone to log in to my email while doing the password reset since he will have no means to know my email password and successfully changed my Apple ID password but how come it still appeared offline and still says that Lost Mode is still pending? Is it possible that the thief was able to delete the iCloud from my phone when he was able to reset the password? Shouldn't my phone stopped appearing in Find My iPhone if that was the case?

He could have removed it but he probably wasn't smart enough if the find my iPhone thing still works.

Your next step is to contact the police and file a report or something as well as report it to your phone carrier.