I've played RS since 2006/2007, and quit right after the citadel update. I have come back after a few years 'cause I heard about OSRS. I am aware it resets your character for OSRS, but that should not be the case for RS3. I was forced to create a new username and it reset my whole character. I wasn't hacked, it's just that everything is reset. Completely fresh character.
I have checked with all my emails and made sure that there was only one account associated with each email address. There is only one. Just to stress this - I am in complete control of my accounts and always have been, this is not a problem with account security.
I am planning on playing OSRS, but i'll be damned if i'm not getting my character back if i'm able to.
Was there an update that messed with the accounts/usernames/whatever? I'm really not sure what to do next. I can supply any other information if I need to.
Jagex will free up your username if you haven't logged in for a while, but I don't think I've ever heard of an account being completely wiped like that.
Sometimes stats will be reset because of botting or bug abuse, but not completely reset like this. My hunch is that you're probably mistaken about logging in with the correct email. That's been the case for other people that have the same issue.
Everybody in old school runescape starts from scratch, your old stats and account should still be around in runescape 3 but you cannot transfer this to old school.