Having very small parts not blued isnt really all that strange, especially if whoever did the park job, was new at doing it, or didnt have the right set up to do the small parts.
My buddy got me into parking things when he took up the challenge, and there was a learning curve (once we got over that, nothing was safe!
). Most things came out great, even right off, but not knowing how, or really wanting to deal with things like small pins, we elected to leave them alone rather than risk losing them. We figured it out later on though (a metal coffee can with a hole in the top for the bead nozzle works wonders).
Its not just the novices that let things slip, even big name gunsmiths dont always get it right. I had a 1911 hard chromed by EGW back in the 90's, and it came back with the barrel, and a couple of the internals still "blue".
Ive also had a couple of rifles parkerized by local smiths before I got into it, and had some small parts/screws that were missed, and came back blue.
Parkerizing is actually very easy to do, once youre set up for it, and you normally get a very nice job, even with very minimal equipment.