I've been playing .62 on and off and I first noticed it when my friend was trying to cut down a tree, he would switch the axe with the stick and the stick would drop, and so would the axe. But the axe is no longer interactable, apart from Inspect. Only fix is to relog.
I don't know the specifics of what he did to cause the bug but with queues sometimes being +20 people I think this bug would become very annoying for frequent players.
I had the same happen to me switching bags. I usually put one of the bags in my hands, then move the stuff over, then use the SWAP option to change bags. I was moving from a child's briefcase to a hunting backpack at the time. So it's either whatever item you have in your hand, if you swap that with something on your character, will cause it to go invisible. This could also be a problem with the invisible guns on players? Maybe they have switched guns whilst double carrying at one time. It could also be a network bubble thing too, in which this action happens outside of your network bubble so that when they enter, your client never registered the switch and shows empty hands in a weapon hold animation.

I also had a teddy bear with 9 damaged SKS rounds inside in Berezino that when I selected TAKE, became non-interactable, on login, they were in my inventory. Could this be server desync?