" This is incorrect, I can't explain why but it had to do with the difference in a visa, a work permit or something like that."
Atta supposedly had a green card. So based on the moronic thoughts of at the time and driven by the memos (wall) Jamie Gorelick sent out, the DoD lawyers and apparently DIA lawyers told the AD team and liason officer LCT Shaffer they could not talk with the FBI regarding Attas "because he was to be treated with the same rights all Americans had". This is at the heart of this whole matter. Yes the Lawyers in the Defense Department went along with the directives handed down by the DoJ. They are on record as to saying paraphrased. They (DoD/DIA) where breaking any civil laws, therefore the AD team was simply told on three occasions to cool it. And Shaffer was told by his DoD Major General to not approach the FBI, with a similiar warning.
Is it believable that the information could have been extracted from databases using pattern analysis, yes (former database designer so I know it is possible). And then there is this interesting tidbit from a New York Times article titled C.I.A. Was Given Data on Hijacker Long Before 9/11 by James Risen and Eric Lichtblau ( February 24, 2004)
American investigators were given the first name and telephone number of one of the Sept. 11 hijackers two and a half years before the attacks on New York and Washington, but the United States appears to have failed to pursue the lead aggressively, American and German officials say.