Sawyer couldn't have hit Sayid, because they didn't know when Sayid was going to light the rocket.
If you use a lit cigarette as a fuse, you only have so much time to run over to Sayid to ambush him, and you would need to know the exact moment the rocket would go off.
Even if he did have a time delay device, I don't believe he could have traversed the distance they needed for a good triangulation in the required time.
Too much terrain in his way. And, Sayid was up on a high plateau.
/may be talking out my ass
