Possessive nouns, the apostrophe, and no 'S'

I was watching an episode of Last Week Tonight With John Oliver. It's an American show hosted by an Englishman.
He displayed a paragraph of text during the show which read, "The Bad Boys Club' T-shirt."
I am confused. The club is called The Bad Boys Club so I figure it's irrelevant that there's not an apostrophe in or after the word Boys. But please can someone explain the lack of an S after the word Club?