How did Stilton find out about Bertie's nightclub visit?

Stilton found out about Bertie's nightclub visit and arrest because his uncle happened to be the magistrate who doled out Bertie's punishment that morning. Stilton's uncle had been to his house in the morning, spotted a photo of Bertie, and revealed the details of Bertie's evening to his nephew. Bertie denies the accusation, saying many people look like him.