I brought a ahri and it disappear, and I cant even refundable. What should I do?

file a ticket with support. top right corner of this screen is a button that says SUPPORT. click it, then click the tab that says "Submit a request".

How does a champion "disappear"?

If you go to the shot, does it still show the "unlock" button?

Is she grayed on the "champions" tab of your profile screen?

Do you still have the IP you supposedly used to buy her?

Have you played her after you bought her already?

If anything goes wrong, your best bet at getting it fixed, if restarting your client doesn't fix it, is submitting a ticket to Support.