During the movie... It happens several times where all three have put down their packpacs and continued on WITHOUT them, to then in the next scene turn to their backpacs and pull something out...

It happens in the scene when they have been falling forever then land in the water... Trevor pulls out Hannah from the water takes her backpac off and they all lie down... Saun sees the birds and desides to follow them... They all leave behind their backpacs following the bird and Saun... In the next scene they are all seen carring their backpacs again... They didn't go back to collect them.

It also occurs when they are sailing across the huge lake... They are setting up the sail when it pulls them into the water, their backpacs aren't on the raft and are not on their backs because it was to hot. Thus they have left their backpacs behind. Yet when Hannah and Trevor are walking trying to find the river, they both magically have their backpacs on again... Are the backpacs invisible for some scenes?