The missing train ticket

Text 1: Valid Today, by Shabnam Qureshi

An original short story extract.

The inspector worked his way down the carriage, clipping tickets with a little silver punch. When he reached the boy by the door, the boy patted his jacket, his jeans, his jacket again, and went white. ‘I had it,’ he said. ‘I swear I had it.’ The inspector waited. A woman tutted. The boy turned out his backpack on the seat: a football sock, a maths book, a squashed banana, and no ticket. The inspector sighed and took out his notebook. Then he paused. Sticking out of the maths book, being used as a bookmark, was a small orange card. He tugged it out, held it up to the light, and checked the date. ‘Return to Bradford,’ he read aloud. ‘Valid today.’ He clipped it, tucked it back between the pages, and moved on without another word, while the boy stared at the book as if it had performed a magic trick.

Explain why the inspector does not write anything in his notebook.