I had no idea that Scott McKenzie had passed on until I came across this thread tonight.
Per Whitburn's book (2003 ed) his real name was Philip Blondheim and that John Phillips wrote LaOTM as well as SF.
My local library used to have a copy of Michelle Phillips's autobiography California Dreamin'. Per said book, I remember reading in it, she, John, and Mr. Blondheim aka Mr. McKenzie, pre M's and P's, were a Greenwich Vlg. folk trio, the Mugwumps (mentioned in "Creeque Alley", the song about the M's and P's origins). This was around 1963. Obviously, Papa John remembered his partnership with Scott McKenzie four years later...
BTW Mackenzie Phillips was by John's first wife IIRC and is thus Chynna's (John and Mitchy's daughter) half-sister.
RIP, Scott (you too, John, Denny, and Cass). See you where there are lots of "people in motion" - with wings.
ixnay