Okay I want to clear some things up here. Photo is of 350 west bound while traveling west coming down to the switch back. This is where he went down, blue arrow is our direction of travel, grey squiggle is where his scrape marks were left on the asphalt, and green is where his bike was up right and park when I came back to check on him. The road was clear, no debris. Curve was to the left and He slid on the right side of his bike. My best guess is that he got intimidated and panicked. I went through the switch back came to a stop at the bottom of the hill off to the side waited for him to come down. After a minute or so I doubled back to see what had happened.