Russ,When was the Acorn removed? I seem to recall it was before the San Francisco Zoo train was removed in 1976 when I was 12 years old.
I'm not sure of the exact date but I do have a photo of the Acorn waiting to be scrapped after removal. It appears the Acorn had been sitting there for some time. The photo is dated 1978. If it was removed prior to 1976, that would fit perfectly.
Here's a You Tube link that will bring back memories for you. The first minute is the MOST important. The rest is a Southern Pacific safety film teaching children NOT to play in the rail yards.
Dangerous Playground
https://www.youtube.com/watch?v=YpCPw1wDKwc
Terry