The Dink Network

int &rock1 = sp(1);
sprite 1 is always dink;
Usually, the sprite number you see in the editor is not the real one, because dink is not there. Probably, if you see 1 in the editor, your sprite will be 2.
I don't know if it's the best ideea, but you could attach a script to every rock, with this:
void main(void)
{
sp_brain(&current_sprite, 91);
}

the secon rock would have:

void main(void)
{
sp_brain(&current_sprite, 92);
}

Then, in your main script
&rock1 = get_sprite_with_this_brain(91, &current_sprite);
&rock2 = get_sprite_with_this_brain(92, &current_sprite);