The article you linked to above says it all, check "Find my iPhone" by locking into your iCloud account on your computer and see if you can  locate the device.

Erase it remotely, so that the next time it comes online, it will be wiped. The phone should also be protected by the Activation Lock feature, it can't be activated without the Apple ID and password that has been used when it has been set up the first time.

Find My iPhone Activation Lock

Report a lost or stolen Apple product

Learn what you can do about your lost or stolen iPhone, iPad, iPod touch, or Mac.

If you have lost or found an Apple product, please contact your local law enforcement agency to report it.

You can take steps to find your lost or stolen iPhone, iPad, iPod touch, or Mac if you've enabled Find My Mac and Find My iPhone apps. Using your Find My apps allows you to put your missing device in Lost Mode, see its location, or erase its data. Other than the Find My iPhone and Find My Mac apps, there is no other Apple service that finds, tracks, or otherwise flags your device for you.

Learn how to locate Apple product serial numbers.