If you go back and look at the crime scene photos, the area that is 10+ feet in, slopes back toward the road. If you are standing on the road in front of where the blue tent is, the side of the road slopes down at about a 40 degree angle to the blue tent. So if the body was back about 15/20 feet originally, then TS Fay came through on Aug. 18th and flooded the area, the water would have drained back toward the road, bringing along with it, anything that wasn't weighed down. Eventually it would have gotten caught up in palm fronds and vines to keep it from floating out to the street.
DH says when he was searching, there was a decomp smell, and they finally found a trash bag about 10 meters away. This was in a different area, off the 417 freeway. The smell would only come and go with the breeze. The only way to get the continued smell was to open the bag. Turns out it was rotten food, but you get the idea...