Following his daughter’s disappearance close to the Texas border, an American man journeys into a disreputable area of Mexico seeking her, uncovering various concealed truths along the way. Chloë Grace Moretz plays the young girl, and Paz Vega portrays her mother. “Not Forgotten,” released in 2009, feels like a combination of “The Flock” and “Borderland,” both decent movies from two years prior. It begins promisin…