Shares Deemed Worthless?

Not to set off any panic here, but I noticed yesterday that BLK shares were no longer appearing in my trading account. That was followed up later in the day with a corporate action from my broker, stating:

"We have received notice that the Ordinary shares of Blackham Resources Limited have been deemed worthless. These shares will be removed from your account."

I cannot find any other trace of this news on this forum, on the Blackham web site, nor via Google new searches.

Is this a big mistake, is there a reassuring explanation, or of course, is this somehow as simple/accurate as the note states?

Thoughts?