well first, you may want to post in Help & Support. This is one of the more tricky sites as it does copy the PvP.net bar and has built-in pop-ups. As a PSA take this as an example to always watch the URL of any site where you are entering your account information.
This one, for example does not begin with the na.leagueoflegends prefix most anything from a the league homepage has, as well as shaving the ending yzi.me which is a personal webpage URL.
Riot should be able to revoke any recent damage done to your account if there has indeed been a hack and/or password change. Just be patient, a ticket will take about a day or two to be responded to in my experience, and stay calm. Luckily there is nothing a hack can actually take away from your account.
Also, if you have a credit/debit card linked to your account be sure to cancel any recent RP charges.