Fizz Bug ?

So I played a game as fizz this morning and at one point quite late in the game my playful/trickster (e) ability was greyed out as if i had never put a skill point into it. It seemed to stay this way until I used another ability. I have played a lot of fizz in the last few days and this is the only time it happened to me, so I'm not sure if it was only a one-time thing or not.