Yeah, and I still don't even know how my account was hacked.
Maybe you exchanged some personal messages with him, and you clicked on some link he sent you.
Scammers often use this tactics to steal login information from their victims, by opening phishing page and entering login details in fake login page.
I also would love to know how to keep any account secure when there is no 2FA option available.
Even 2FA is not perfect protection, but you could improve security by adding 2FA (not sms related) to your email address.
In forum profile settings you can modify it by visiting Account Related Settings, and enabling option to Limit IP retention, BUT there are some risks when doing this and you can lock your profile.
You can also sign a bitcoin message in forum to prove ownership of your account.