[GAMEPLAY] Lux E grayed out halfway through a game and became unusable.

So just finished a game where I was playing mid Lux with her star guardian skin on(not sure if that matters). Never happened before this match but part way through, E turned a dull colour like it was on cooldown and became unusable for the rest of the game (was a ranked match) my team still managed to win luckily. I didn't die before it happened but I was in a teamfight so I'm not sure if one of my teammates or an enemy casting on me caused the bug but teams were Lux, Udyr, Morgana, Caitlyn, Irelia vrs Malzahar, Karma, Nunu, Jinx and Garen. Also E was my only ability maxed out at the time that it happened. I restarted client mid-game and then restarted PC. Still remained unclickable... Tried playing a custom game solo vrs bots and had no problems with her E that time.