Lost lp for a minor reason

I just had a ranked game as Renekton. About 15-20 minutes into the game, my wifi shut down for no reason. After being afk for ~10 minutes, I come back on to see that I'm two levels behind from my laning opponent. Then, I played for 15 minutes and ended up winning the game. However, for afking, I lost 16 lp (I ended 13/5 that 40 minute game with 269 cs). This feels a little unfair since I decided to spend my time trying to play the game instead of just quitting and letting my team deal with it.