First off, I found it VERY strange that Charlie first says he doesn't remember anything, and then immediately afterwards says that they only wanted Claire... The two are mutually exclusive. How does he know that, if he can't remember it?
Second, the underground facility (if there is one) could explain the creature. Big enough to move trees, but never seen? I thought: "Subterranean!" It also moves with a sound like a subway...
As for predicting rain, many watches these days (such as Suunto's H6, or High Gear's Summit) have built-in altimeter/barometers, and can graph the barometric pressure over a 24 hour period, and/or sound an alarm when the pressure drops suddenly (indicating a coming rain). It's possible both that Locke could have prepared himself for a Walkabout with such an item, or that he is simply perceptive enough to have noticed the signs of the oncoming rain...
So it really might be as simple a trick as looking at his watch! (Especially if it has a vibrating alarm, instead of a sounding one!)
But hey, in
Lost, who knows? Pretty much anything is possible! I'll be really upset if the "sickness" is hallucinations/delusions caused by some poison/radiation, and it "was all in their minds"!
