Your account is probably been deleted because it clears out any in-active accounts. You may need to make a new account.
I doubt anyone can get their username back once it's been deleted because they don't want anyone to think it's an imposter of some sort.
You couldn't try to contact a mod to see if they can recover it but it may just be easier to make a new account.
Well it's certain that your account hasn't been deleted as you are here right now. Even after a long while, so you might not have been inactive enough for the account to be automatically deleted at or after 18 months of inactivity (if I do remember correctly). However, on the 'old' forum, there used to be a password change through the forum. I think this might be the issue you're having, as you might have attempted to change your in-game password through there at some point, only it would only change your forum password through that method. I suggest going to the Home page of the Feral Heart site and changing your password through 'Forgotten Password'. Once your password is reset, it will reset through both forum and in-game and you should be able to access your account in-game as well. I hope things work out for the better, come back if you need help or the situation has been resolved or still needs resolving.
You are most welcome! Go have yourself some more great times!