The Times’ story was a rare animal, a bombshell based on a source whose identity is unknown even to people at the news organization that broke the story. Although anonymous sources are commonly used by journalists to elicit sensitive information, reporters almost always know their identity, even if they don’t disclose their names to readers or viewers.

That doesn’t appear to be the case in the Times’ story, which carried the bylines of four reporters, including Craig and David Barstow, an investigative reporter who has won three Pulitzer Prizes.

While Craig declined to discuss her understanding of who sent the Trump documents, Times deputy executive editor Matt Purdy was definitive: “We do not know the identity of the source.”

In hindsight, however, that may have been among the least problematic elements behind the documents Craig received that Friday, Sept. 23. The major challenge was authenticating the three pages and placing them in the proper context to understand Trump’s tax strategy at the time, said Dean Baquet, the newspaper’s executive editor.