There is an article in the Warren County Observer 27 April 1961 in which Widen describes the incident. The article was written just before his trip to Germany in 1961.
Widen says his normal plane "The Great Gut" was out for a spark-plug job, so he had to fly a spare plane that was performing pretty badly. The left wheel door would not quite close, which produced a lot of drag and he could not get full power in the left engine. He describes the dog fight, where he got on the tail of an ME 109 and Hafner got on his tail. One interesting comment is where he came down. He says "I came down near the Tunis airdrome, held by the Germans into what was like a back bay,
one foot of water and two feet of mud." He goes on to describe the planned meeting with Hafner's brother in Germany, when his wings were to be returned.
He may have come in the Sebkhet er Riana (Sabkhet Arina).
http://www.lib.utexas.edu/maps/jog/a...87-nj32-15.jpg
The Tunisian desert did have a lot of P-38s at that point in the war so there were probably a lot of choices for the photo. If his plane was also in two feet of mud and a foot of water it was probably not quite as dramatic a photo.