Mike and Josh sarcastically singing The National Anthem.
After Josh disappears, Heather finds a bundle of twigs outside their tent. While in the movie this and its contents are horrifying, amusingly, Heather's reaction is NOPE and just chucks it away rather than open it. The actress had to be told by the crew to go back and open it. It's a very realistic reaction in a genre full of people walking into dangerous things because the movies need to get a scare in.