I cannot find this

PLOT: a boy gets dropped off in the woods by his mother, i think it was close to his grandfather’s house. He is in a tent and hears noises and sees people. he thinks it is his lost sister. he searches through the dark, he finds her and there is a car/ truck driving through the woods towards them. he leaves her in the tent and she is gone (i think). and there is a real twist at the end.