For weeks, Transportation Secretary Sean Duffy has derided the New York City subway, repeatedly making fear-mongering assertions that the nation’s biggest transit system is unsafe.

He has characterized the subway as a hellscape, even though it is used by more than four million riders a day and underpins the financial and cultural capital of the United States. He has threatened to withhold federal funding for the trains unless crime rates decrease, even though crime rates are decreasing.

And on Friday, he and Eric Adams, the increasingly Trump-aligned mayor of New York City, rode the subway together, at Mr. Adams’s invitation. Where or when, exactly, was a bit of a mystery.

What ensued was a cat-and-mouse game involving Mr. Duffy; Mr. Adams; Janno Lieber, the head of the Metropolitan Transportation Authority; and a cadre of angry train supporters seeking to confront Mr. Duffy on their home turf.

“So far, no show, it’s been a ‘Where’s Waldo’ game,” said Mr. Lieber, who, with his pro-transit posse, was left pursuing whatever tips they could glean from the internet, and their own network of sources. He spoke to reporters who had gathered expectantly on the platform at the Brooklyn Borough Hall station.

After noting that the M.T.A. carries more people in a day than the country’s aviation system, Mr. Lieber expressed hope that Mr. Duffy would get a proper briefing. He then got on a No. 4 train and went on his way.