I got a leaverbuster: My laptop updated on it's own...

I had exactly 28 lp and I was doing so good at the beginning until my laptop automatically updated. Well I came back, at 27 v 23 when my team was winning. I actually got 2 more kills and 3 deaths and we won. I was expecting 0lp but no I got -15LP + leaverbuster. What do i do?