secure folder is usually only for Developers and people whole work with samsung or partners if there is anything important in there. i am sorry to tell you but you can not recover or unlock unless you have a password also samsung cant help either i would suggest to change your account and maybe by miracle you can back up the folder somewhere else.
Secure Folder is not only for developers, users can generate one if they wish and using password/biometrics/pattern the use can add/remove files or apps. It doesn't get connected to cloud or anything and is strictly ON-DEVICE so it's got less chance of being meddled with.
Hence there is a chance that the OP is indeed hacked. Not certain but one possibility.
To the OP. Back up the phone and factory reset, see if that clears the Sec.Folder. If it does and for some reason it returns, then immediately report to samsung members app > get help > error report and title it something along the line of 'suspected hacking' and explain that you didn't make the folder.
