Nebulous
Legend
These things happen. As long as you tell the players you stuffed up and that you'll play it by the rules from now on, then it won't matter. If you let them keep on doing it then it might break the game.
I hate having to double check on spells, I leave up to them for these low level common spells to do them correctly, and they usually do, but every once in a while something slides by us that really should't.