It's bad losing a phone to theft is frustrating. If this happens to you then immediately report the theft to your mobile carrier to block your SIM card and not to access an unauthorized person. Though it's easy to find out stolen or lost phone by using IMEI or Phone Number. It also help you to track someone's phone location if you already installed an app. Stay using and consider to install an app or feature to protect your next device from theft. All the best!