I Found the Entwives!

[the phantom]

You know, I think I'll go ahead and throw a big punch. Let's get this thing going.

Someone or something untied the rope in that scene. That's the only explanation.

In Lorien, Tolkien specifically mentions that the Elves had to untie the ropes from the trees and then draw them in. Tolkien also mentions more than once that Sam was very skilled with ropes and knots. And then there is the rope incident. What is the point of it?! Did Tolkien have it happen just to contradict himself? No, obviously not. I don't think Tolkien would contradict the logic that his own words created if there wasn't a point to it.

Plus, if it was indeed magic rope that could come untied via thoughts/wishes, don't you think the Elves would've warned them about it? "Oh, and be careful using this rope. A flick of your mind can cause it to come untied." I mean, isn't that a pretty important bit of info to leave out?

Plus, Haldir is a show off. We have evidence of that. Remember this, from FOTR, Lothlorien-

"This is how we cross! Follow me!" He made his end of the rope fast about another tree, and then ran lightly along it, over the river and back again, as if he were on a road.
"I can walk this path," said Legolas; "but the others have not this skill. Must they swim?"

That part always annoyed me. Haldir knew good and well that everyone in the Fellowship couldn't walk on a rope, so what was the point of doing that little stunt? Showing off, obviously. And since we're dealing with such a show off, don't you think that if the ropes could be untied magically he would've done so?

Answer- yes.

But he didn't. Further proof that ropes, even from Lothlorien, don't just untie themselves.

Someone or something was in that gully and untied Sam's rope.

It's a fact.