Syndra's W interaction with Soraka silence

In game I noticed that when I had a minion grabbed with my W (Force of Will), Soraka proceeded to silence me. However, when I walked out of her silence, I noticed I could not recast my W to throw the minion. Even if I was not inside the Equinox.

The strange thing is, the ability icon showed I could recast it, but the cooldown had already begun, and was displayed on top of the icon like any other normal ability on cooldown would.

TL;DR: Casting Equinox (or possibly silencing Syndra as a whole) while she has something grabbed with her W, will cause her to be unable to cast it again to throw said thing.

Steps to perform the bug: Choose Syndra and Soraka on either team

Rank W on Syndra, and E on Soraka

Have Syndra grab a minion, and have Soraka silence them while the minion is still grabbed.

Have Syndra walk out of the Equinox and try to cast W again, only to be unable to do so.

Note: I am not sure if this is the case for other silences such as Garen's. What I mean by this is Garen could silence Syndra while she has something grabbed, and after the silence she could possibly still recast her W. I have not yet tested this.