So apparently it should be possible to do radioisotope analysis of feathers to find how old they are.
The Birds of North America Online page on IBWO says that Agey and Heinzmann reported seeing IBWO and in 1968 "they retrieved small dark feathers from a downed cavity and a white feather, which was identified by Alexander Wetmore as the innermost secondary of an Ivory-billed Woodpecker (Agey and Heinzmann 1971a, 1971b). The feathers and Wetmore’s letter are in the collections at the University of Florida Museum of Natural History."
Apparently this finding was controversial - I think I remember reading somewhere that (although I can't find it) that this was partly because a similar feather was reported missing from a specimen.
So if feather dating is possible, why hasn't it been done on this one, to see if it was really shed in the late 60s or much earlier?
Apparently there has been a DNA study of this feather - this page
http://www.si.edu/research/spotlight/04_14.html#Woodpecker
from the Smithsonian says
"NMNH scientists Robert Fleischer and Carla Dove and colleagues began the project as a simple barcoding effort to add the Ivory-billed Woodpecker sequence to the Barcode of Life Database (BoLD). In addition, they wanted to know whether a feather found in 1968 in Florida was really an Ivory-billed Woodpecker feather."
It then talks about how their studies showed that the Cuban IBWO was a separate species. However I can't find anything that says whether they confirmed that the 1968 feather was IBWO. It's not mentioned in their paper. Does anyone know what the outcome was?
And if they were already analysing it, why didn't they date it?