Was in a Co-op game, and then I DC and see the "Attempting to Reconnect" box.

I wait for 2 minutes or so, then i restart my client. When I logged back on, there was no reconnect button and it was as if I never played a game.

BUT WHO WAS PHONE?

seriously though

You may be experiencing some very simple problems. Your internet may simply not be able support the game at the time due to over use, or, your firewall may have started to block league of legends.

Add an exception by logging into your firewall/router/modem to insure that League of Legends is allowed connection.