I'm really surprised that no one chimed in on this one. I did a little more digging and believe I figured it out.
After the #343 was returned from the C&S, it probably was indeed never used in revenue service even though it was returned in serviceable condition. It probably wasn't needed. When Hollywood needed a locomotive, all of the inservice small power was either Montrose, Gunnison, or Durango. It was probably easier to bring the #343 back to life than to ship a locomotive from those locations.
There is a picture in the "Narrow Gauge Pictorial, Vol.1" by Richard Kindig taken Sept. 1 1940 of the #343 in the Alamosa yards. Though the siderods are removed, the locomotive is otherwise complete with all appliances intact, like a locomotive that hasn't been sitting for long.
The #343 was cut up in 1941.
Any other comments or corrections are welcome.
Regards,
Donald Foster