Also bare in mind the truly wealthiest persons on the planet you would never find on any public list. Their wealth alone dwarfs those of the public known riches.
Yes, of course. Countless trillions of dollars in wealth are just sitting around somewhere and no one's ever noticed them or wondered about them. Totally plausible!
You are right. They are smart enough to make and keep trillions of dollars, but not smart enough to hide it from you! Ever hear of money laundering? The money doesn't just fall off the grid, it is made to look like something else. Just ask UBS, HSBC, Wachovia, etc....