Booted out of Ranked Champ Select
So, I was booted out of a Ranked Champ Select lobby.
I got a game invite, pressed accept, got booted out of the screen And it gave me a L for my first game in my promotions to S5. 
So, I was booted out of a Ranked Champ Select lobby.
I got a game invite, pressed accept, got booted out of the screen And it gave me a L for my first game in my promotions to S5. 
Is it possible you did not lock in a champion or ban?
I am sure. It was loading into Champ Select, everybody was declaring their picks and once it hit 0, it booted me out into the queue lobby with my duo and I had to wait 5 minutes and i had a loss on my promos to S5.
Freezing or crashing in champ select then returning to the lobby is usually a result of a failure to establish a stable connection to the servers.
Champ Select in all modes requires a more steady connection than the lobby as picks (and bans for Draft) are processed in real-time. This is why it's more vulnerable to disconnect there.