Hey,
There's been a lot of misinformation / incorrect assumptions on the thread so I just wanted to clarify that if you have not yet upgraded to a Jagex account and a hijacker upgrades your account, you need to contact support here.
Once we verify ownership of the account, if you are the owner we will get your account back to you.
Where I think people are getting confused is the stance we have on accounts that are already Jagex accounts (and have been made so by the original owner), which is that there is no manual recovery option, to prevent hijackers from accessing Jagex accounts secured with 2FA.
I hope this helps.