Why was i kicked out of champ select?

So i was in ranked queue and it was my turn to pick but i couldn't figure out what to pick so i chose lux and i had 5 seconds left to lock in and i click lock in right as the timer said 5 seconds and then i got kicked out of the lobby and got a timer to wait now before i can queue again, but i'm just confused on why i got kicked before timer went out if i already chose my champion?!?!