Walking in one direction all day and ending up at that SAME LOG.
How about the VERY last shot, after the camera is dropped? Is that part of the rocks, or a face-up dead body partly hidden by the stone wall? Also, it's pretty safe to assume something grabbed Heather, causing her to drop the camera.
Someone or somethingwas attacking the tent.
After all that walking through the forest, they come across an abandoned house... with the interior covered in bloody handprints.
The outro at the ending credits. It's pretty ominous, ambient like, and very, very disturbing with all the sound effects. As if the Blair Witch is stalking you in the woods, and fits perfectly to the film's general theme. Antonio Cora, props to you.
Josh knocking over one of the cairns. Even though nothing scary happens immediately, you know at this point that all three characters are doomed.
On the forth day, Heather wakes up and finds three little cairns around their tent.