Opera GX on what operating system?
When Opera started, did it show that it just updated? If so, what version do you have now and what version did you have last? You can find that out by going in to the install folder (path shown at the URL opera://about) and looking at the newest and last version folders.
I was no longer logged in. After I logged in, everything was just gone,
Are you referring being logged in to your Opera account and are you using Opera Sync?
Did you recently change your password for operating system account or change your computer name in your system settings?