Twice now i've hit a wall whilst gm'ing and have had no idea what to do. In two different games i've run my overly bright players have been armed with wonderfully deadly grenades and no throwing skill whatsoever. In both occasions they've missed hitting their intended target altogether getting no successes after defaulting to the attribute. Now with bullets or even rockets I can figure out what happened and rule what happened null sweat. Thrown grenades though are another thing, the main rules assume you made at least one success on your throw but I have no idea what to do with a total miss, and due to the nature of grenades you have to know where they went in a miss. (although if it's all 1's it lands at their feet) Any ideas?

As you normally would, you would roll the die for scatter direction and roll for distance it travels. And since there were no successes to reduce the distance of the scatter, it's totally up to the dice where the grenade goes.