Varus piercing arrow would not work?

i just got done with a 5v5 on summoner rift, playing as varus, about 10 minutes into the game i realized my Q piercing arrow would not work, which was odd because it was working before i had died, i couldn't hot key to use it,, and i couldn't click to cast,, i did not try to disconnect and reconnect to the game, but once it stopped working, it didn't come back for use the entire game