^Sounds like the police just weren't interested in a rusted out car hulk without any reason to be. They only got interested after the remains were found. Apparently the car was found by the dive group....and from what I gather, it was just brought up more or less for the adventure. ( or maybe cleaning up the lake..I dunno)
Speculation so far is she simply went off the road ...probably slid off in bad weather. The road hugs the shore pretty close to the lake there.
Below the viewpoint is where it was supposed to have been found. See the google map pic
here.