I thought the same thing happened to me a while back, but really, I was just on the wrong account.
If you have multiple accounts, did you accidentally log into the wrong one?
And have you shared your password with anyone who would have deleted your characters? You should never share your password, but if you did, another person with access to your account may be linked to the issue.
I'm not sure there is a way to get your characters back, other than recreating them, I'm afraid.