If you've signed a message before with your account then you're lufky there's a possibility that you can have to claim it back by providing thesame process in signing a message provided you've staked your bitcoin address, i think now members will begin to understand the usefulness and benefit of signing a message using your bitcoin address, but I must say this that tou jave also been careless with the handling of your account for it to have been taken by another user, maybe you once use their device to log in or been careless and let a third party ser your password when trying to log in, but i have a strong indication that this must be been through your negligence to security measures.