If a CIA black flight went down over land it'd likely be found within a day or two, all the more so since the area it crashed in was not heavily forested so it could be located on satellite photos and very likely had some kind of on board emergency transponder for just such events. DNA will last that long and more.
The CIA having DNA for the guy is more likely then having his dental records, if he even has any anywhere. A spy can lift a DNA sample off any number of objects, tooth brush works for example, you basically have to break into the guys dentist office to get dental information and god only knows when the person last saw a dentist who kept records. The US managed to get Bin Ladens DNA, lots of stuff is possible. Collection is not hard, analysis can be done with portable equipment, not that this is even a requirement since they might have had his DNA for years beforehand. The real life US intelligence budget is in the range of 85 billion dollars and all, you can buy all kinds of toys with that much money to blow.
"This cult of special forces is as sensible as to form a Royal Corps of Tree Climbers and say that no soldier who does not wear its green hat with a bunch of oak leaves stuck in it should be expected to climb a tree"
— Field Marshal William Slim 1956