Comeback victory

So I was playing a ranked match and my internet cut out. Frantically figure out the problem, internet comes back up. Get back into game and I'm only level 3 to my lanes level 8, seems like a tough road ahead. Slow play, team is doing great.

End up having an awesome game as shown, 5-0-4 and we win the game. I was met at the stats screen with -18 LP, a D- score, and a message saying "Due to AFK tendencies" I was not awarded anything and even lost LP. WTF.

Is there a thread I can read more into this? Holy moly I lost LP after that. It felt so good coming back and winning the game. Now my question is what's the point? This tells me that if my internet ever cuts out, why try and hurry back into the game?

Why suffer through being extremely under-leveled and toxic players just to lose LP even though you helped the team win? This has to be some kind of problem with others.

TL:DR; Internet cut out, got back into game, won game, lost LP WTF