If you don't have a back-up of your data or have a device that you can access, then there is nothing we can do. Mozilla has no access to your data. https://support.mozilla.org/en-US/kb/access-mozilla-services-firefox-account '''What makes Mozilla accounts different?''' At Mozilla, we put your privacy first. '''Any data you store on our servers is encrypted with your password, making it impossible for anyone without your password to read your data—even Mozilla.''' The benefit of this is that no one can mine your data to create a profile of you. However, it does require that you make a password that is both strong and memorable. If you forget your password and reset it, your storage is wiped clean and replaced with what is currently saved in Firefox on your devices.