Oh, I disagree! If they don't find her...it is not going to damage the prosecution. In my opinion, since the water flooded the area after she was buried...she could have been literally washed into a deeper area easily depending upon how deep she was buried, how far away from the water she was originally, and other factors.
Mark K. does have a point, but he has to also understand that while it would be better for only one person to go search as a precaution for preventing someone pushing her further into the earth...independent searches have already taken place there. Having more boots on the ground isn't going to do any more damage than could have already happened.