Roger Shawyer is not even a physicist, he is an aerospace engineer which makes this even more impressive if this turns out to be true
Darwin was a geologist.
The cosmic background radiation was discovered by astronomers (not by physicists)
Coca cola was created by accident when a pharmacist was trying to find a way to cure headaches, and lab assistants spilled a mixture of coca leaves and cola nuts (and some other trace components) into his carbonated water.
Percy Spencer worked as a radio engineer for Raytheon on combat equipment for the DoD, and noticed that the candy bar in his pocket melted when he walked in front of a magnetron. This lead to him inventing the microwave.
There are all kinds of breakthroughs made in science by accident, or by people working other specialties.