Had to include the man who helped found Quantas. I mentioned another Australian mystery man on the other thread: Harold Lassiter, who died presumably still seeking the biggest gold reef in the world outside of Johannesburg.
There was an interesting book about the Le Prince disappearance - THE MISSING REEL - which does look a bit at Thomas Edison as a possible suspect, but says there is no smoking gun.
Le Prince (for those who don't recall him) was one of the fathers of modern cinema cameras.
Another inventor - genius who vanished (suicide/accident/murder?) was the creator of the Diesel Engine, Rudolf Diesel, who vanished when on a cross-channel steamer in 1913 headed for England (possibly to offer his revolutionary engine to the British Navy, thus making him a target for Wilhelmine agents).
Or David Lang who was said to have disappeared before the very eyes of his wife, children and his friend the Judge, in USA in 1800's, or was this just a cover-up by the judge and the family.
Some students on disappearances point out the Lang story sounds similar to a short account written by Ambrose Bierce about the disappearance of a man named Williamson in Kentucky in 1854 (Lang vanished in Tennessee) and also the disappearance of a boy named Oliver Larch, who vanished one night going to a well.
Indiana Dunes Women
Nice list, but who was Robert Beutel (if you wish to say)?