Thom Powers's documentary "Mr. Apology" is an artful rumination on guilt and forgiveness. Its subject is the New York City artist Allan Bridge, who ran a confessional phone message line from 1980 until his death in 1995. Callers would use this now-dated technology to leave or listen to anonymously recorded apologies for everything from marital infidelity to murder. "For 15 years you could tune in at any given time and hear the most profound storytelling on that line," Mr. Powers now says. "For a documentary filmmaker that’s an inspiration." Some would call the film a must-see, and yet it is a can't-see. It exists only as some raw footage and proposals in a box on Mr. Powers's shelf. Paul Vandecarr reports.