Desert Echoes by Abdi Nazemian

Fifteen-year-old Kam is head over heels for Ash, the boy who swept him off his feet. But his family and best friend, Bodie, are worried. They struggle to understand Ash. He also has a habit of disappearing, at times for days. When Ash asks Kam to join him on a trip to Joshua Tree, the two of them walk off into the sunset ... but only Kam returns.
 
Two years later, Kam is still left with a hole in his heart and too many unanswered questions. So it feels like fate when a school trip takes him back to Joshua Tree. On the trip, Kam wants to find closure about what happened to Ash, but instead finds himself in danger of facing a similar fate. In the desert, Kam must reckon with the truth of his past relationship – and the possibility of opening himself up to love once again.