Keyboard and Mouse stop functioning during game.

I was playing an ARAM, and during the game, my keyboard and mouse stopped functioning within the game window. While this wouldn't be as surprising, what happened was that I was unable to do anything inside the game window (as in, couldn't click anything or type in chat), but was still able to access my computer and do everything normally outside of that.

The game ended before I could try rejoining (having left the game to try and rejoin it), but figured I would state what happened anyways. This issue has never happened to me before, so if anyone knows a way to fix this if it happens again, please let me know.

Thanks a lot!