@BillRM,
There have been other hoaxes that were not discovered for over 40 years. This one for example.
Piltdown man is one of the most famous frauds in the history of science. In 1912 Charles Dawson discovered the first of two skulls found in the Piltdown quarry in Sussex, England, skulls of an apparently primitive hominid, an ancestor of man. Piltdown man, or Eoanthropus dawsoni to use his scientific name, was a sensation. He was the expected "missing link" a mixture of human and ape with the noble brow of Homo sapiens and a primitive jaw. Best of all, he was British!
As the years went by and new finds of ancient hominids were made, Piltdown man became an anomaly that didn't fit in, a creature without a place in the human family tree. Finally, in 1953, the truth came out. Piltdown man was a hoax, the most ancient of people who never were.