Draco went to London on a dare. No wand, no broom, no Floo powder, just some Muggle money (fifty pounds) in his pocket and Harry's words ("you'd be lost, Malfoy") ringing in his ears.
He wasn't lost. He had only to stay for the afternoon. But he had to buy something, or nobody (Harry) would believe him.
Draco joined a queue, bought a ticket for some sort of play. The stub would do for proof.
The lights went down. The curtain rose. The trailers rolled. The movie started. Draco's mouth dropped open.
Three days later, Draco was still in London.