I didn't think that it was very graphic... Yes there were some scenes that might have put it at PG-13 or Rated R, but it wan't bad at all imo in terms of a graphic nature - not compared to most movies out there anyway.
share"Unrated" doesn't necessarily mean "graphic." The rating system in the US is administered by the motion picture industry through the MPAA, a trade group, not by the government, and no movie is required by law to be rated. A movie's producers have to pay the cost of the rating process, which can be very expensive, and since it's run by the industry, it tends to be more lenient toward big-budget movies from the major studios. Many low-budget independent movies are unrated simply because the producers don't think the benefit of a rating is worth the cost and the hassle.
Although it's not required by law, in practice a movie must be rated to get national distribution. The purpose of the ratings is to guide parents in selecting movies for their children to see, so ratings are important primarily to the large national theatre chains where children normally see movies. But urban "art house" theatres, where a movie like David Searching would most likely be shown, cater almost exclusively to adults, so they rarely require that a movie have an MPAA rating.