Right clicked on rope with the three charms all in same bag. The four items disappeared. The message "You receive Bracelet of Lucky Charms" displayed. But nothing, nada, nil. Not any of bags, not in crafting bags, not on person, just wasn't given to me. I checked immediately after the award, so no chance of accidentally selling it or dropping it etc. Logged off, logged back in, still nada. Only two things I can think of, almost literally exactly the same time, my flying pegasus mount ended and got removed from inventory (did that lock the Inv or something for a moment?), and I right clicked the rope in a small bag, not the main bag. However, all bags had space free. Pretty basic foobar.
This is something that happens a lot. You need to check on your Diplo clothing tab and you should find it there. Somethings will go to diplo or crafting bags when they go in inventory and not the main bags. If it is not on your Diplo wrist and not in Diplo bags then submit a /petition.