When you have an item in your backpack (or in your Clothes) an you take it in your hand with using the hot-bar, if you disconect (or crash server) when you reconnect you get a second time this item. One in your hand and the other in your backpack or clothes (depending where you put it). The item don't lose attachment, and are completely usable separately. I hope you understand me. Sorry if i have bad english. (I'm French)