OK, so I am not SURE if this is a bug.
I had acquired 30+ plasma pistols from dead aliens. I sold 20 or so (down to 10 left) to raise funds. Two of my troops stationed at that base had plasma pistols equipped at the time. Later after auto missioning a few routine UFO recovery missions I went back and looked. I now have zero plasma pistols in inventory, and my troops are fighting empty-handed.
Note this is not plasma pistol AMMO I am talking about here, but the pistols themselves.
Log info to follow later when I get home. If this is expected behavior please ignore.