LP loss for a 4v5 loss

For 2 games in a row now, my mid laner had a huge lead and just disconnected. Lost a total of 40 LP and nothing ever happens. Riot auto bans someone for using offensive language, something you can just mute and not pay attention to. But something that ACTUALLY affects the game gets no attention. If you didn't duo with the afk person, your loss should be prevented and the person should get a temporary ban from ranked games for the first offense. If it becomes regular, the bans should become more lengthy/permanent.