It's probably in a lake somewhere. I live in Minnesota, which is called the "Land of 10,000 Lakes". Actually, it's closer to 20,000, but we're modest. :)

What's known is that the driver, after hitting the cyclist, drove to his mother's workplace, and she left with him. The car he was driving has not been seen since. If it was driven into a remote lake somewhere, it will probably never be found.

Ground scanning radar can look into lakes down to about 60 feet deep and find metal objects rather easily.

One would think a murder investigation would (a) know this, and (b) have the ability to get data from a military or private satellite, both before and after the suspected incident.

Failing that, tracking data from the pairs phones would likely indicate which lake, and probably which part of the lake even.

Maybe. But that sort of thing is expensive for a court case, especially when there is sufficient evidence for conviction already.

The driver was convicted of vehicular homicide (max five years), and leaving the scene of an accident. He can't be forced to testify about the location of the car (Fifth Amendment), and I don't know if he was charged with obstruction of justice. His mother was charged with obstruction-type charges, and her case hasn't been tried yet.