From the time we saw the Black Rock, we’ve wondered how in the heck something like that could have gotten into the middle of the island. The same question comes up when you think about Eko’s Plane. How could it have gotten SO off course that that it made it to the South Pacific all the way from Africa?
You know how? I think it’s because the islands are moving around, or they might even be time shifting. In fact, if you go back far enough, the continents did shift around a lot, so the time shifting idea makes even more sense.
That would explain the reason that Ben and The Others say once you leave you won’t be able to get back.