Just my opinion, but I feel that the cases are unrelated because I feel in Jessica's case, the description is not accurate.
There may have been a van in the area, in Jessica's case, because a van was seen on video, but I think the ball was dropped when all eggs were put in the basket concerning the description of the vehicle and person. That person who took Jessica, in my opinion, got away with it, because Everybody was searching for 2 Bogus things, the descriptions of the vehicle and perp.
Now, if there were individual sketches, that look similar, made from both the husband and wife eye witnesses, and one composite drawing was made from that, it is possible they had a someone or two in mind, so therefore, those 2 eyewitnesses who happen to have been together that night, it would seem that the sketch is legit, right, because their accounts correlate/match, right?
I feel the police department and the public have been lead astray, and the inaccuracies are apparent to me, particularly with the fact that 4 months have now passed and there has been no sighting of Jessica, of said perp and of said vehicle.
Now the question leads to why would there be inaccuracies in the sketch and the vehicle?
IMOO.