Lost your phone, but do not have the IMEI number handy to register a complaint. Nothing to worry if you have Android OS. Google stores the IMEI number of each of the phones you have used to install Android using your gmail id. If your phone is not lost you can retrieve this number by calling *#06# and the IMEI number will be displayed on the phone’s screen. Alternatively, you can open device Settings – About Phone – Status and long-press the IMEI number to copy it to the clipboard.
If you have however lost your phone but did not record the IMEI number beforehand, you can still retrieve the number from your Google Account. Just go to google.com/settings, sign-in with your Google account and expand the Android tab. Here you will see of all Android devices that are connected to your Google Account and it will list the IMEI number of your phone as well.