So far, I have only stated what the rules say, technically, the game should stand, because it wasn't a sitter as declared by the TuS Rules.
My personal opinion:
That last grenade, without a doubt was lame, it was horrible lol, but in no way was he trying to do a sitter on purpose, he chose a shot he thought would bounce around safe and kill without sitting, it did stop motion, but it did not exceed the limit.
Unfortunately, that last grenade is perfectly legal, I think the fact that it got stuck was accidental, he threw it with enough force and angle it should bounce around and blow near the worm, unfortunately, the bounces were horrible and it stopped motion for a split second, but not long enough to make it illegal.
My advice, try and find a hide where this kind of shot won't kill you like this so easy, you took the risk by hiding there, as frustrating as it is, dC never done anything illegal.