So where is the White Rock?

When MiB and Sawyer entered the cave, there were two rocks on the scale, one white, one black.

But we've seen another block rock, the boat. And it's play a significant part, IMO, to warrent a balanced role for another white rock.

Could the island itself be the other white rock?

What happened to Desmonds boat? He left but came back. Did someone else take it?

And in the flash sideways, he was on the plane. So he either never went to the island or he was able to leave.

But Jacob is the balance of MiB.

Man in Black. Jacobs nemisis.

That's what they call him in the pop ups on the re run episodes.

Maybe it was the plane!

They left in a small power boat. Come to think of it, there's no way they could have made it very far in that.