After the plane crashes and Khonanesta finds Sam and Bonnie, Sam has a line of blood trickling down the right side of his face. As the trio begin their adventure, just about a minute later, the blood is gone.
A hand-drawn star map shows the handle of the Big Dipper pointing to the North Star (which is in the Little Dipper), and Khonanesta describes using the Big Dipper to find the North Star as shown on the map. This would not work. Actually the two stars in the front of the bowl of the Big Dipper point to the North Star. The handle points to various directions depending on the season, but never towards the North Star.
When the two kids cut themselves loose from a rope tying them back-to-back to a tree, it's obvious that they could have easily wriggled free from under the rope. It was loosely wrapped around them as they sat with their backs to the tree, nothing else was tied, not their hands or feet, so they could have easily gotten out from under it.