There has been some conflicting communication.
The pretty well buried official announcement in the Gems of War forum says:
The public facing announcement in the Puzzle Quest 3 forum trying to play down the issue says:
Note that players haven’t been notified in any meaningful way. This is currently still only known by frequent forum readers that dive deep into threads, it hasn’t even been mentioned in the weekly event post. It’s somewhat safe to assume that “a couple of weeks” is a similar gross exaggeration, just like “anybody who wants to craft it”. There’s no way players could obtain the “highly discounted” 2000 diamonds in a single week, and IP2 knows this very well.
TL;DR: The special recipe is supposed to disappear way before you could actually craft it.