[Gameplay] A glitch with gragas

In a game I used my Q and it went off cooldown then the q reverted to 0 mana cost and 0 on the cool down and I was no longer able to use it for the rest of the game.I seemed to happen after it was placed in a large minion group,because it went away right as it went into the large group of minions. I've seen Gragas play since the patch so i'm not sure if its just me or under certain circumstances .