My iPhone 5S stolen. What do I do?

I lost my iphone in a public place yesterday. I called to check if anyone had turned it in. Nothing. Unluckily, I was going to sell my iPhone 5S tomorrow, so I took off all security passcodes and may or may not have turned off the "Find My iPhone" App. I still got on the app in case it is on. My phone is considered "Offline" according to the Find My iPhone App reader on iCloud (?). When I call it, it goes straight to voicemail. I went ahead and reported it as lost on iCloud with a password lock and sent the default message of if someone has found it to return it for a reward with a phone number to contact. Then, I went back to the place it was stolen, talked to the manager, and then filed a police report, as recommended by the manager. They said they'll pull up videos today or tomorrow depending on how busy they are to look into who took it. They took the offense seriously.

Question: If my phone is offline and Find My iPhone app is off… Does that mean that the phone will still lock itself and be unable to be used by the person who took it? Or only if the app was on?

Question: If I report the serial code to the police like they said, how will that help me in getting my phone back, if ever?

Put it in lost mode: http://www.justtext.com/messageboards/20140224185823.html

Here's what you do. Use your insurance to replace the phone that you lost and then in the future don't be so careless with the replacement phone.