When you cannot find your Android phone or iPhone, you need to:
If you cannot find your mobile phone, the first thing you need to do is to ensure whether the device is really lost or just misplaced. You can simply confirm that by calling the device. Or you can use Find My iPhone or Android Device Manager to track the device. If you make sure that the device is truly gone, you need to take action right away.
Once you lose your phone, the most important thing is to change the passcodes of the accounts that you have signed in on the device. To achieve that, you can login to your accounts on computer and then go with the instructions on the screen to change the passwords. This would protect the security of your personal information and property.
After changing the passcodes, the next step you need to do is to contact your carrier and tell it that the phone is lost or stolen. Then the carrier will stop the service and start the process of getting your number transferred to a new device. Now the people who steal your phone will not be able to do anything on your phone so you do not need to worry that your families or friends would be cheated.
If the phone you lose is a work phone, you cannot forget to inform your employer. That's because the phone saves the information of your clients and colleagues and work-related files. So it would be a big problem if the thief reveals these data. What's more, after knowing the truth, your company can take preventive steps to secure its data. For example, your company might be able to delete the data on your phone remotely.
At last, remember to erase the data on your phone which can 100% guarantee the security of your phone data. But you are only suggested to do this operation when you absolutely ensure that the phone is stolen cause these erased data is unable to be recovered unless you have backed up them to your personal computer in advance.