...i just realised that the story is a slight copy of Cannibal Holocaust (which someone mentioned in the 'what movie has made you vomit' post, so i decided to check it out)
Cannibal Holocaust (1979)
In the beginning of this film we meet a documentary team of three young men and a young woman. They are heading for the south-American jungle to search for real cannibals. After a while the crew is reported missing and a rescue team is send from the US. This team gets in touch with an amazon tribe called the Tree-people. The tree-people gives them the only remains of the first crew - the filmrolls containing the material this crew shot during their search for real cannibals. Back in the US we get to see these films. We now get to see exactly what happened to the first crew.
Blair Witch Project (1999)
Three film students travel to Maryland to make a student film about a local urban legend... The Blair Witch. The three went into the woods on a two day hike to find the Blair Witch, and never came back. One year later, the students film and video was found in the woods. The footage was compiled and made into a movie. The Blair Witch Project.