I'm just that good, boys.
I never held a Hydra Launcher.It's comforting to know even the server doesn't know WTF is going on sometimes.
I'm gonna take an assumption and say it came on your Scorpion destroyed. It was actually destroyed by a Hydra on your team, but for some reason the game gives a couple frames between when it's health reaches zero and when it awards the kill. So the game saw that you damaged the vehicle last, and it awarded you with killing the Scorpion, but it saw that the Hydra was the actual weapon to drop the health down to zero. Since you didn't actually fire the Hydra, it knew 0/0 acts as 0% accuracy.