I dunno how it works on the US, as a don't invest there. But when I buy some commodity, I get a certificate from the holder saying that it is on their physical possession.

That certificate ensures the commodity is mine even if the holder gets bankrupt or some other disaster. Not having it there would be fraud, and my government does go around checking it.

I have a quite strong suspicion that this is universal. But well, I haven't checked this.