[CRASH] I was in a Flex and got «Disconnected» (Kicked out)

So, I was in a Flex match and after 8-10 minutes I got «Disconnected». By disconnected I mean that I had a loading bar on my screen non-stop and I was unable to move (same for my duo partner). But my connection was fine and my league of legends client was allowing me to start another game (I could click the «play» button). I couldn't see the game in my match history and I couldn't join or reconnect. I think someone in the other team kicked us of the game. How can I report that? or what can I do when this happen?

Thank you