The normal approach to Mammoth-Yosemite airport is from the south-east, landing on runway 27 (facing 270 degrees) in order to avoid high terrain near the airport. There are two recommended entries to final approach: 1) Direct from the Owens Valley, or 2) from the north, passing Mono Lake, a right turn to the south, and then a right turn to the north-west onto final in the Crowley Lake area. As you can see from the MMH approach chart below, it can be like threading a needle. There is only one safe way in and one safe way out.
It's possible he was trying for option 2, but had a problem over Yosemite (icing, engine, health issue, etc.)
The snow is getting deeper each day in the high country; finding wreckage will be difficult until next summer.
http://www.fltplan.com/AwDisplayAppChart...&WINDOW=YES 
