Natural History Museum Scientist Fired Because He Saw Nessie

Yeah, this actually happened.

Denys Tucker was a top scientist at the Natural History Museum, called on the the most brilliant people that worked there. In 1960, he made a claim in New Science Magazine saying he had seen the Loch Ness Monster. Yes, a scientist actually saw a cryptid! What happened? The museum fired him! He then fought a legal battle for seven years because he felt he was wrongfully dismissed from his job. Tucker passed away in 2009, and recently the files on his claim have come forth because of the Freedom of Information laws.
Denys Tucker, scientist who saw a monster in Loch Ness
from Mirror Online

Tucker's sighting of a monster happened in 1959. He was on the shore of Loch Ness when he saw what he called an "unnamed animal" break the surface of the water. He said in New Science Magazine that he believed he had actually seen an Elasmosaurus, a plesiosaur that lived in the Late Cretaceous Period about 70 million years ago. He also said "I am quite satisfied that we have in Loch Ness one of the most exciting and important findings of British zoology." Some people did not believe that Tucker even saw anything. But, I think he did.
Elasmosaurus

You can see the original article on the story here.