trying to look for an "official FBI statement."
Because there isn't one? The article in r/conservative links to the relevant Washington post article, which includes all the links to their previous reporting. The report about nuclear related documents is here. The source spoke on the condition of anonymity:

A document describing a foreign government’s military defenses, including its nuclear capabilities, was found by FBI agents who searched former president Donald Trump’s Mar-a-Lago residence and private club last month, according to people familiar with the matter, underscoring concerns among U.S. intelligence officials about classified material stashed in the Florida property.

Some of the seized documents detail top-secret U.S. operations so closely guarded that many senior national security officials are kept in the dark about them. Only the president, some members of his Cabinet or a near-Cabinet-level official could authorize other government officials to know details of these special-access programs, according to people familiar with the search, who spoke on the condition of anonymity to describe sensitive details of an ongoing investigation.

whether you personally find that to be a credible report or not is totally your business, and judging by your tone in guessing the answer is no. But nobody is making the claim that you are complaining about.