Autofilled bottom WTF!?

In the last ranked solo/duo game my roles were jungle and top lane. But i autofilled bottom lane when autofill was not even activated. I am not very good at AD carry role, my main roles are top lane and jungle. But the one thing that i really don't understand is why i autofilled when the autofill was protected? I think it is somekind of bug splat. However due to the uncomfortable role play i lost 20LP and it was not even my fault. You owe me 20LP riot games thank you so much.