Asong writer who wrote a song for an artist and it became the number one hit and he forgot about it, who was he?

It’s none other than the bearded proto-hippie ‘Eden Ahbez’. 

In 1947, Ahbez approached Nat "King" Cole's manager backstage at the Lincoln Theaterin Los Angeles and handed him the music for his song, "Nature Boy". Cole began playing the song for live audiences to much acclaim, but needed to track down its author before releasing his recording of it.

Ahbez was discovered living under the Hollywood Sign and became the focus of a media frenzy when Cole's version of "Nature Boy" shot to No. 1 on the Billboard charts and remained there for eight consecutive weeks during the summer of 1948. In early 1948, RKO Radio Pictures paid Ahbez $10,000 for the rights to “Nature Boy” to use as the theme song for their film The Boy With Green Hair and he was credited as the song’s composer on the opening titles of the film.