I have been there many many times. There is a pack station and a little store/restaurant there. There are lots of trails into the wilderness areas around there. My question is how he got down there was that even on his flight plan.
My understanding is he was searching for a dry lake east of there in NV on his flight. I doubt anyone knows why he was in the Mammoth area but I believe he could have just come west to follow 395 for his fight home or maybe for the scenery.
I would think it would be very difficult to spot wreckage in that area even from the air unless you were right on top of it.