Why weren't clothes left behind?

I thought exactly the same thing.

And where the hell was Kirk Cameron?

It would make the disappearance of the passengers a bit too obvious and would cut out a lot of pages of dialogue of the characters speculating what had happened. Plus it would look too much like The Rapture.

If you've ever read Misery, there's a reference to the writer in that remembering a kids game called 'Can You?', a story telling game where each kid has to make up part of a story on the spot. King writes that the part of the story that the kids makes up doesn't have to make complete sense, or even much sense, as long as its riveting and the other kids buy into it. I'm pretty sure King has been playing this game most of his life.

You're right. It's immediately obvious. But in writing it's what's known as a conceit, which I found a pretty good definition for:

"A CONCEIT in a cinematic sense is the premise that the audience accepts in order for the story to take place."

http://messageboard.donedealpro.com/boards/archive/index.php/t-58739.html

In the case of TL you can readily see why the clothes weren't there: they'd have literally covered the view of the objects the director obviously wanted us to see. It would have been less immediate/dramatic to see endless and quite large piles of clothes mixed in with the watches, pins, etc.

Another reason for such a conceit is that it lends an air of mystery to the disappearances. Without the clothes it's not completely clear that the person has been plucked out of existence--call it what you will. Perhaps we are supposed to suspect they've simply been abducted leaving some crazy things behind.

Either way, it may work in a technically convenient way but not in a story sense. Conceits are often as obvious and as badly-handled as is exposition, being too trite and a little too convenient for most people to swallow.

But TL had bigger problems than that.