User blog comment:Cryptomania/Primarch Rubinek??/@comment-10514705-20120429140619

Cyrptomania, your opinion is relies on anecdotal evidence just as much as the Lexicanum page. I don't believe the author was on to something especially as, and Lexicanum states: "Primarch Rubineck is not mentioned anywhere else"

In fact, given the official ruling by GW, the Lost Primarch's will never be revealed. Authors of the Horus Heresy series have been allowed to hint at their fates and make mention of them (since during the twilight of the Great Crusade the fates of these Primarch's, and their Legions, would be recent events).

The Horus Heresy novels are of course much more recent in their publication, and therefore any facts in those books take precedence over a 13 year old short story which mentions a single name without any context. Particularly as the fluff has shifted and changed since early 3rd Edition.