This happens in both LIVE and PBE

So after using AP yi and AD yi I have gotten this bug.

After using Alpha strike if the minion dies as i cast it, I continue with a cast and the icon shows up as ready for use. (mana is used and damage is done)

1. use Alpha strike on a minion about to die.
2. watch the animation, and see the CD timer is static
3. wait to use it again

Has this simple bug happened to anyone else?

Thanks for reporting but this bug has been happening for a very long time now. This only happens when you click the spell very fast and it does not have time to record you're action.

-Best of luck, Google