Range is abstract in this game. Near is "A few steps away", Short is "Up to 20-30 yards and Long is "Up to a few hundred yards. In order to have the grenade playable at all, you need to think a little bit abstract.
If you throw a grenade to Short range (from you) it lands normally Near its target. Since you throw the grenade at the target, the grenades momentum is away from you so the grenade would bounce a little bit away from the target or to one side (left or right). Sure of course a grenade can fall "a few steps" short. Since Short is 20-30 yards. I would rule that if the thrower do the normal thing when they throw a grenade, they are not hit by the blast. This "taking cover" is a little bit cinematic, I know, but MYZ is a little bit a cinematic game. So as long as they players throw the grenade, throw a doorway, and then immediately taking cover behind the wall or throwing the grenade and duck behind a low wall or something, they are safe. It looks good and the player needs to be a little creative if they are going to use such dangerous explosives.
But if one of my player would throw a grenade and do nothing else but standing there, I would rule that they are hit by the blast. Mostly because I think it is very stupid, not very creative. This can of course be done with a normal grenade (it has a blast power of 3 to those in short range), not wise, but possible. Molotov is safe, since it only has a blast power of 6 and doesn't do damage to short damage.
A miss on the other hand is a miss and should have consequences. How to handle this .This depends on the situation of course, but you could rule that the grenade land Short from the target and randomly determine in which direction. If the grenade has landed short towards you, that probably means that you have hit a pipe or a bird when you throw the grenade and it bounces back. Such a bad luck. Perhaps you the group should give the grenade to someone with a high Agility and/or Shoot skill.
Or you could make a trap with it. Safer, unless the trap-maker misses when he creates the trap of course. Then it is not so safe for him.
“I’d say thistles, but nobody listens to me, anyway.” - Eeyore