A multi-million dollar company like Riot can find a way to stop this
This is unbearable. It's been happening a lot lately. Yesterday I played 3 Coop vs AI games and got one bot in my team, two bots in my team and in another one there were three bots in my team. We couldn't even surrender as when my teammate initiated a surrender vote it wouldn't be succesful because the bots don't vote. It was the first time I've ever wanted to just quit the game in process, but I didn't want to take penalties. But, it was pitiful.
All Riot has to do is have a will to want to stop it. They have the records of the games, data about the player/bot behavior to be able to analyze it, identify suspect accounts and request a human interaction at some point before the next game. They could add one of those CAPTCHA verifications where they have to type in the number shown in a graphic or something. If not that, there has to be a solution and a will to find it.
Perhaps, Riot prefers people playing PvP and don't mind if players quit Coop v AI and move to Normals and Ranked. I don't know how the evil doers startup the bot games, but we need to make harder if not impossible so they lose incentive to cheat.