You can't held people responsible for UNMARKED classified information, end of story. Otherwise government can imprison anyone after declaring ANYTHING classified.
Here is the DoD standard
(b) As used in subsection (a) of this section— The term “classified information” means information which, at the time of a violation of this section, is, for reasons of national security, specifically designated by a United States Government Agency for limited or restricted dissemination or distribution;
Every classified document shall show on the first page, title page, or front cover (hereafter referred to as “the face of the document”), the originating DoD Component and office and the date of the document’s origin. This information shall be clear enough to allow someone receiving the document to contact the preparing office if issues or questions about the classification arise."
PORTION MARKS. Every classified document shall show, as clearly as is possible, which information in it is classified and at what level."
http://www.dtic.mil/whs/directives/corres/pdf/520001_vol2.pdf
Were these standards met? If no, then you were a victim of fake news from ZH, a notorious fake news site.