Gragas Q Would Not Cast

Hello. Recently, I was playing a game as Gragas on Summoner's Rift. I don't know exactly when this happened or what caused it, so I know this is less than helpful. But at one point, while all of our inhibs were down, my Q ceased to function. It was still available to cast, but it was listed as costing 0 mana with a 0 second cooldown. This problem persisted for about 5-10 minutes, even after I tried disconnecting and reconnecting to the game, straight through until we lost. If it helps, team comps were Blue: Gragas Taric Twisted Fate Sivir Gangplank

Red: Nasus Kha'Zix Vladmir Blitzcrank Ezreal