Graves Q bug???

I played Graves last night on my brand new mafia skin, and i realized that in a couple occasions my q didn't do any dmg to the enemy (ies) even though they were well in my q range. In the first occasion it was one enemy, in the second occasion there were 2, i was pretty sure that i hit them, the WERE in range but 0 dmg. Could that be a possible bug?? Has anyone else had that problem before?