Because no archival photos and footage of most of the Pol Pot era exists, films about the Cambodian genocide have had to use creative ways to tell what happened. The Oscar-nominated documentary ‘The Missing Picture’ from a couple of years ago used clay figurines as a visual complement to the narration. John Pirozzi’s ‘Don’t Think I’ve Forgotten’ uses the popular music of Cambodia in the ’60s and ’70s (and the artists who made it) to detail the country’s trajectory.