Unknown Error - Lost a Promotional Match

I queued up for a ranked match and accepted it. While we were banning, someone on the other team froze at 0 seconds. Then, it kicked me out of the match, gave me the following error, and I lost a promotional match. This does not make any sense. How have I lost the match?

Unknown Error

An unknown error has occurred

Sorry about that. We've sent a report to the server.

If your continue encountering this error you may want to check the support site or forum for more information.

Edit: I restarted League of Legends and there was a small update. Could this have been the reason for the unknown error?