How does dodging work?

Hey folks!

Played a game of Thresh earlier this day which ended in a loss. Thing is, I dodged this game... Literally, I exited my client during champion select, and when I logged back on to take the penalty it instead gave me a "reconnect" button. I was so confused... I thought the system was created to not begin the game if a person didn't connect? The clock was still ticking down towards "game start" when I walked outta there, expecting a 3 lp loss but instead getting an 11 lp loss (predicted bad outcome of the match since they had an obvious 5-man premade centered around Yasuo and my teammates were flaming from the very beginning).

Now, this didn't really matter too much to me as I regained 3x the lost lp in my following victory, but it's still frustrating that I had to play a game of 30 minutes simply because the client didn't let me dodge.

Hope someone can help explain this to me, as I'm slightly blown away by this. What if I'd just decided to not play another game? I would have unknowingly forced my teammates to play a 4v5. Is there some sort of rule that you can't dodge after you've locked in your champion? My match history can be viewed here, I'm talking about the 2nd match.

Addition: I posted this earlier on "gameplay" but it was deleted. I figured something tied directly to the game's champion select would be fitting there but apparently not...

I got replies on the other topic that I should have dodged before the "bang" but I did. That's why I wrote this topic, I had 10 seconds left. Please read everything guys...