Ah, you’re talking about the individual who made this post in which they confused the Articles of Confederation (PDF link) with the Constitution. I’ll quote that part of the linked post:
How is it not in the text? “Each state retains its sovereignty, freedom, and independence, and every power, jurisdiction, and right, which is not by this Confederation expressly delegated to the United States, in Congress assembled. ”
Mind you, that post was made just a touch over three years ago.