Ranked losses due to dc/afk

I was in a game today in which my team was winning 4 to 0. Our midlaner then dc'd (after lecturing us not to) but we managed to keep a good lead (i myself was 8/0/6). He then returned, fed the enemy team, and dc'd again, causing us to lose. I find it appalling that Riot has done nothing to prevent losses like this. I lost 23 lp and one of my teammates got demoted. If you agree pls upvote