Veigar Ult Deals No Damage, Does Not Go On Cooldown

So I was just minding my own business, Qing people during a teamfight when their Katarina flashed in to ult my team. I responded by ulting her back. She built glass cannon and I was fed. It felt like a million other moments playing my beloved evil Yordle, but this time something different happened. The projectile launched, she Shunpo'd away to a minion, obviously fearful of it and probably hoping that it wouldn't 100->0 her (it would have). It tracked her down, and collided with her, and then... Nothing... No collision animation, no damage, no nothing. I was thoroughly confused by this and looked down at my cooldown bar. Apparently, my ult had not in fact gone on cooldown.

Now, I don't know why this happened. My first thought was maybe packet loss or something. I haven't had problems on this internet connection in years though and more importantly, the Katarina reactively Shunpo'd away, halting her ult and giving up a double kill to save her own skin; it wasn't just on my end. Luckily that fight I just hit R again and that time it worked properly, but If this bug could be exploited, it would be horrendously broken. Primordial Burst is one of the most powerful abilities in the game. People will do anything in their power to avoid it or at least avoid the rest of Veigar's burst if it's coming at them. You can easily trigger flashes, barriers, heals, spell shields, Wind Walls, everything. I'm genuinely concerned for the existence of malicious Veigar users that use false Primordial Bursts to bait out defensive spells so that they could then use the real one against the now defenseless target.