Macworld UK published an article explaining how to find the IMEI of an iPhone. This number used to be etched on the back of the device, and it’s now under the SIM tray. But there are other ways you an find it: by dialing a secret code in the Phone app, or in the Settings app.
But the article left out another way. You can find the IMEI in iTunes, even if you no longer have the phone, as long as you’ve backed it up.
To do this, choose iTunes > Preferences, click Devices, then hover your cursor over one of the backups. You’ll see all sorts of information, including the phone number, serial number, and IMEI.
Yet another reason why you should back up your iPhone in iTunes…