NSA leak suspect was ratted out by an office printer

It's very hard for me to understand how the author of this article got to "[printer tracking codes are] exactly how the FBI says it was able to find and arrest her less than a month later", when nothing in the affidavit says that this evidence was used in the investigation and the reporter doesn't quote any source saying that it was. The argument seems to be that, because the government could have had access to such evidence, it was in fact used.

The article implicitly accuses the government of deliberately concealing this investigative method in its affidavit (which is certainly possible and could be akin to deceptions and omissions that have happened before), yet doesn't mention that the FBI has not, in fact, admitted to doing so. (Nor did the author report having asked the agency!)

Extensive discussion: https://news.ycombinator.com/item?id=14494818