When you created your Runemate account, you would have set up an email on the account.
If Runemate detects you logging in to a new location, it sends an email to your registered email asking you to confirm it is you wishing to log in. Once you click on the link, it takes you to your profile/setup page where it whitelists the new IP address.
If you no longer have access to that email address, your best bet is to try and log in to the original account and change the email address to a new one.
If you cannot access the account from the location you first set it up on and you don't have access to the email address then you are out of luck, unless a staff member can verify it is truly you by your IP address and resets it for you.
@Arbiter should be able to help you here.