Gencon was issuing warnings about this a good few months before it happened. They had announcements everywhere.
Indiana business journal
Every gaming group and blog were announcing it. I even actually saw it on the news at one point albeit briefly.
What did you want a personal phone call?
I agree... it was everywhere. Personally I saw it on:
The main page of the Gen Con website
The official Gen Con forums
Facebook (Gen Con page, multiple Gen Con groups, multiple gaming groups, news reports...)
Television (as I am local)
Other local sources
So I have no idea how much more they could have done. They hit every single source of information they could have. At that point, the blame can not be on the company. They have covered their bases.