Had an almost exact experience some months ago. Was riding my bike home and saw a bloke looking unconscious just off the path, its a smaller less busy town but it was evident many had walked past.
I was a little nervous as i approached as he was a biggish young guy but wasnt moving, I called out as i approached and got no response, i then called the Ambo's and gave him a nudge and eventually a shake.
He started to show signs of awareness after a few minutes, I just talked to him until the Ambo's arrived then left him in those hero's hands.
I understand peoples reticence to approach, but these are human beings for fvcks sake