486 was last used by the D&RGW on November 4, 1961.
On November 2 it worked west from Durango to Chama.
On November 3 it worked as a helper out of Chama:
11/3/61
Extra West to Durango
Called 930 am
494 Shock, Waterman
480 Connor, S. Smith
Extra East to Alamosa
Called 1015am
483 Holt, Gibbs
484 Hardy, Luster
486 Sisemore, Cooper (Helper - returned to Chama)
11/4/61
Extra East to Alamosa
Called 1130am
486 Sisemore, Cooper - called to load stock in Chama.
Called 1pm
491 Faucette, Cunningham
488 R. Morgan, Weirick
All engines ran to Alamosa.
So, it seems 486's last duty was on a 3-engine stock train out of Chama.
486 sat for some time on the dead line in Alamosa before going to Canon City in around 1966.
For more info, I guess we'll have to wait for Jerry Day's book.