Here's a mediocre theory... Oceanic 777 got sliced in half by a worm hole, which caused the turbulence and ultimately split the plane in half. A good chunk went into another dimension, while the rest just dropped into the Pacific Ocean. The "Others" are not exactly bad guys, but just normal islanders from another dimension and just as afraid of Jack's crew, as Jack's crew is afraid of them. The reason why nobody is looking for them, is because in this world, they don't know Oceanic 777 bombed. But in the other world (the world/dimension they come from, a rescue search has found the rest of the survivors who did not get zapped into the alternate universe (where Jack's crew is))
