This weird theory just popped into my head.
What if the reason the Island can not be seen by the outside world is because it doesn't exist,
anymore.
The Hanso experiments happened in the 70s right? Well what if thats where the Losties are now? Theres no sign of any modern technology on the Island unless it was brought there, and the Island is a strange mish mash of times and eras, from the big statues to Hurley's VW hippy van.
My theory is that when the plane went down, it went over some Bermuda Triangle type thing, and got sucked back in time. Perhaps this time displacement is caused by the EM field generated on the Island.
Desmond can somehow see the future because he has a connection with the outside world, so he can "see" what has already happened.
Also, the plane they found in the pacific, it
is our flight 815, and they
are our losties on board.
Remember Naomi said that they found the plane on the bottom of the ocean and little robots went down and saw all the bodies, they never actually dragged them up. Id assume all the bodies were damaged due to water. So what if the plane and people went back 30, maybe 40 years, and then continued living there so the time over laps. Then something happened to the Island causing it to be destroyed which is why the outside world can not see it, but the plane and the losties "survived". So they found the plane, but it hadnt been there for 40 days, it had been there for 40 years.
The others probably know this and to some extent can control it and communicate with the future, even travel to it; probably though some sort of work hole, the very same one the Lostie plane accidentally fell through.
The Russian could have known Locke in the real world, but he was much younger and he travels to the Island further into his future, by the looks of him perhaps from some post-Apocalyptic Snake Plisken world
What you think? Probably not but the idea made me think.