Apparently, the removal of the rail was not complete. If you look at photos taken in 1939 at Alpine, or the west portal, the rails and switches are mostly still in place. In fact photos taken into the 1950's still show rails in place at Alpine.
As to pictures of a train on the Pitkin branch, I know that Dorman's Gunnison book shows a stock extra at Pitkin with two or more C-16's. I believe that normal service on the line during D&RGW days was provided by a mixed train up until some time in the late 1920's.