Hacked account

So my bud and I were hanging out studying and we decided to mess around and play league during a break. He hasn't played in a bit because he mains adcs and doesn't like the current meta. He was banned permanently for third party software. He had never been in trouble before so we thought it was weird and checked his match history. There were a few games during the time he was taking a break from league. No one else knows his password so it most have been hacked. Are there any options for account recovery after it was hacked? I know it sounds like he was hacking for ranked but he hasn't played ranked in years and the hacker for some reason only played aram. A game mode which he also never plays. So ya if anyone knows what we can do to get his skins back it would be helpful. Thanks!