I found it by re-navigating through the Pit Barrel Forum:
As you can see from the link, it has changed taxonomy a bit from /forum/grills-and-smokers/charcoal/pit-barre-cooker/ to /forum/charcoal-drums-barrels-and-bullet-smokers/pit-barre-cooker/
So my point is that a typical way to handle this, that is both good for existing customers who have bookmarked sections of the site and external links that point to the old urls, is to setup a "redirect". That way if someone tries to go to the old url it points them automatically to the new url without hitting the "Invalid Page URL. If this is an error and the page should exist, please contact the system administrator and tell them how you got this message."
Good luck and best wishes...
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