[GAMEPLAY] Soraka E and Kassadin Riftwalk

I was in the middle of a game, playing as Soraka. I noticed that one of the enemies was using teleport , so I waited a little bit, and used E on it, so when they came out, they would be silenced. The enemy teleporting was Kassadin and he riftwalked out of my E before the E closed. This is a problem, because I placed the E to snare the target, but not only was he not snared, but he used an ability to escape it, even though he was supposed to be silenced.

Riot please.