I reformatted by system and installed new operating system. I wanted to login into my Facebook account from my desktop. It has been years since I used my account from desktop. Login allows you to use phone number as login name. Well, I had used my phone number with another account. Only option I had left was to somehow find login email address. All Facebook instructions and help pages could not give me straight answer to what to where I can find login email address. I realized that I had been getting notification emails from Facebook, that must be my login email. Here are the steps to find Facebook login email from your mobile phone app.