Had the same. I died because I was stuck against a wall and when I came back both my pistol and revolver attachments were gone :( The silencer was great too.

Happened to me as well. I went to a different floor and my attachments disappeared. Tried loading the latest save (in which I had already picked up the attachments) and they were still gone.

I'm glad that I am not the only one with this problem.

I have same problem.
This bug is not fixed.

I found one pattern in missing silencer etc. and tried one thing which worked.
the problem on my side with those missing things is always with particular saving station, the one which is exactly in front of kiosks that selling flashlight, silencer, faster reload of shotgun and lubricant for magnum. So, if you experiencing missing items after you load the save from that station I am offering you a solution that been working for me: if you need to quit game here (before entering server room) do not buy any of those items, save here and quit. When you resume the game buy everything you need and than safely play until the next save station that is has no problems before.