Tons of skillshot abilities are confirmed not to make a sound or noise when hit in the fog of war.
This includes Varus, Gnar, Ezreal, Aatrox, Bard, Yasuo, Brand. None of them make a sound when their abilities are hit in a brush or fog of war. Please Riot fix this asap, it's a huge bug for players who scout or think they missed a skillshot when they actually didn't. I've lost a bunch of kills as Varus because I believe I missed the target who was backing in a brush.
Other threads have been created as well. Here's a video a fellow summoner posted: https://www.youtube.com/watch?v=kDN3ge8Uyrs

hits a tornado in the fog of war, it BOTH makes a sound AND shows you the tornado animation of them being knocked up.