Calling it "confidential information" from los alamos is probably just a trick to evoke thoughts and assumptions that he was stealing nuclear secrets.

In reality, given the pattern of intimidation and lies from this government, it was probably something innocuous that was trumped up even just to be a violation of an NDA (e.g. maybe a draft of a not-yet-published non-unusual research paper that included an author from Los Alamos), or else this government would have emphasized the sensitive or dangerous nature of that "confidential information".