I remember these lanterns in place into the early 70's. They were neat--D&RGW marked and all. As for railfans stealing them, I remember that the ones I examined were riveted onto the switchstand, probably for that very reason.
As to what happened to them, I remember seeing some that had been thrown into a standard gauge gon with other scrap metal. That was about the time they disappeared from the yard. I remember trying to figure out a way to climb into that gon and lifting a couple of them--after all, they were scrap and needed saving. But, lacking the courage or realizing that I was sure to be caught, I did not do so.