I just had my mouse stop working half-way through a match.
When I returned, everyone was 6 levels higher than me. And my team was ahead in kills. I was wondering "how?" but the answer soon presented itself when an idiotic jarvan jumped on me while I was 3 levels lower than him yes, and he did have a snowball item, but he also got cut off from his own team, jumped into the middle of my team, proceeded to take his sweet time(enough to derp for 3 seconds after realizing I was gonna die) and after which I revived.
Ended with a score of 1/2/8 and both deaths were from before I disconnected, took part in only 2 teamfight, which were almost complete stomps in our favor.
Also, a hilarious exchange before my mouse broke, I killed a cho, with ignite and by spending all my mana and the enemy twitch started chasing me, I barely got under the tower, when I die. My laning partner, an Amumu, attacks twitch, getting killed in the process too, and our Karthus picked up the Twitch kill with his ulti.
That twitch was actually pretty bad, considering he was 9 summoner levels ahead of me. I got first blood off him with no losses, my only kill too.
EDIT: I have 21 mastery points now, should I keep the 15% pen or go for presence of the master?