There is a lot of evidence to disprove that claim. Here is some:
1. Arkansas Times article, which says Cornell search team member Jim Bednarz has seen several pileated woodpeckers with an abnormal amount of white wing feathers in the Cache River refuge, and he believes there is an isolated population of pileated woodpeckers in the Cache river bottoms who have an uncharacteristic amount of white on their wing feathers.
2. At the 2005 AOU meeting, Ken Rosenberg of the Cornell team publicly admitted that several abnormal Pileateds were seen in the search area, and he mentioned pictures of them.
3. Birding expert Noel Snyder saw an abnormal Pileated in Florida that looked very much like an Ivory-bill.
4. Abnormal Pileateds have also been mistaken for Ivory-bills in Texas.
5. In January 2006, Cornell search team volunteer Sharon Stiteler said in an interview:
I've seen footage of this abnormal Pileated. It's got like two or three feathers on the back that are white that shouldn't be white.6. Here is Cornell's web page featuring photos of abnormal Pileateds found in the search area.