The vanishing Halloween sentence

Mysterious stuff. TPM has the teaser, and author Marshall says there'll be a follow-up. A story running in today's WaPo was updated to remove the italicized clause in the following paragraph:

On July 12, the day Cheney and Libby flew together from Norfolk, the vice president instructed his aide to alert reporters of an attack launched that morning on Wilson's credibility by Fleischer, according to a well-placed source.