Trace your lost phone: No App needed. Google, Find My Device.
Can’t find your mobile phone? You can use the Google Device Manager to locate your phone provided it's switched on and is online. You'll be able to ring the device, see the location or maybe erase the phone content remotely. You'll be able to even find the IMEI number of the lost phone from your Google Account.
You can locate your phone by even searching on Google for 'locate my phone' or 'find my phone' and Sign In to your Google account.
Note: This applies to Android phones and tablets only. You don't need any third-party App to be installed on your Android device for locating it. Apple iPhone users can check icloud.com/#find and more at Apple Support.