Here is John Kerry's statement:
Particularly after a week marked by unspeakable tragedy, we are all relieved and grateful knowing that Theo Curtis is coming home after so much time held in the clutches of Jabhat Al-Nusrah.
For two years, this young American has been separated from his family. Finally he is returning home. Theos mother, whom weve known from Massachusetts and with whom weve worked during this horrific period, simply refused to give up and has worked indefatigably to keep hope alive that this day could be a reality.
Over these last two years, the United States reached out to more than two dozen countries asking for urgent help from anyone who might have tools, influence, or leverage to help secure Theo's release and the release of any Americans held hostage in Syria.
Every waking hour, our thoughts and our faith remain with the Americans still held hostage and with their families, and we continue to use every diplomatic, intelligence, and military tool at our disposal to find them and bring our fellow citizens home.
http://www.state.gov/secretary/remarks/2014/08/230836.htm
Quatar is interesting as the mediator. They have been accused of funding this organization and even ISIS. Yet, they have been trying to be seen as a "respectable" country - whether by having a soccer team that plays against European and British teams or with Turkey, being seen as one of the conduits for getting information to and from Hamas and possibly having them use their leverage with Hamas.
Here, they have very likely saved this young man's life. It is interesting that his release will get a fraction of the attention of the gruesome murder.