Mike,
I remember reading that the D&RGW actually inspected the K-28's and didn't want them after seeing them.
I'll try to dig out the source, but it was not an offical D&RGW Document.
The only thing I can think of is that in 1942 the D&RGW sold (39) Passenger Cars to Mexico. The Shavano and The Chili Line were both money loosers and were finally taken off the timetable in 1941/42.
They still had the (3) K-28's for Daily San Juan Service plus the 483, 484, 485 and 488 that were also outfitted for San Juan Service. The had (20) K-36 / K-37's. Why in the world would they even want (7) Worn out K-28's back? As a Business decision it probably made sense to leave the "Off the Books". Any little excuse to reject them would have worked, even if they weren't worn out.
I wish I had a time machine to save them though...
Kevin Cook