I have now remembered why the girl on the station platform saw my wallet (as the actress said to the Bishop).
She wanted to see my ticket (which was in my wallet) to check something because the details on her ticket didn't match up with what was displaying on the departure boards. Of course, she found quite quickly that my ticket didn't tell her anything bar where I was travelling from and to. I did see her ticket though, which was one of the advanced ones and was able to point out that she'd bought a ticket for the day before. Gimp.