The skull came from a 500 year old human and a decades-old orangutan. I don't understand what you're trying to say with all the "based on evolution as a fact" stuff. Creationists can't tell the difference between a skull from a man who lived in the 1400s and an orangutan who lived in the 1800s?
Creationist scientists did not debunk the Piltdown man because the creationist movement didn't gather much steam until the 1990s, based on the work of Dr. Michael Behe, Dr. William Dembski, and Dr. David Berlinski.
There were creationists in the scientific field from 1912 to 1953, but they were not in the field of archaeology, nor were they really a scientific movement at that time (at the very least, not like those who subscribe to the theory of evolution). And besides, Piltdown Man's skull was locked up in a museum for those 40 years. Would evolutionists allow it to go into the hands of someone actively looking to discredit their theories?
It was discredited because an evolutionist endeavored to discover just how old the skull was. Some evolutionists theorized that it was 500,000 years old, maybe this was just so jolly ol' England could tout itself as the birthplace of civilization. When the evolutionist used fluorine testing and discovered that the human portion was 500 years old and the orangutan portion was less than 100 years old, the jig was up. Hide the Piltdown man! We never believed in Piltdown man! Eurasia! Eastasia!
Creationists prior to the 1990s were simply uninvolved in the
How does a creationist know that a skull is 500 years old?
And not much point if they were. The relevant field is palaeontology.
Creationists still aren't a scientific movement.