[Gameplay] A visual bug bug with Cassiopeia's Miasma

Unfortunately I don't have any video footage of the actual bug, but I was playing a game Ryze, and had to face a Cassiopeia, however it was very hard for the do go up against her, since I had no clue where her W ability was. The spell simply didn't appear on my screen, I could see the animation but nothing was on the ground, I asked my teammates about it several times, but noone answered, so I don't know if it was a bug exclusive to me or if they had it too.. Btw. I'm running on windows 10, dunno if that makes a difference!

Thanks!

Yours sincerely Donfeta