Hello Jim! Yes, this is heartbraking. It is torture for us modelgun fans as we love our guns to be as realistic as possible, and for me realistic markings are the crown of a good model.
Anyway I have seen something similar on 1990s MGC ABS M16 models where the Colt markings were permanently removed, looking like milled off or burnt out of the ABS plastic. I do not have a picture I am afraid.