[Gameplay] Can't cast Lux E

Was playing Lux in an ARAM, fired an E and then repeatedly pressed the button to get it to detonate as soon as it could. Once the ball got to target, it just disappeared. Initially, I thought it was a vision bug, since it was in the bush, but then realized that for the rest of the game, my E was stuck in that greyed-out, "the ball is in transit you can't cast this", thing going on. Even after waiting for cooldown, and dying a few times, it stayed greyed-out and uncastable.