When Harry was on the Hogwarts Express trying to look through Draco’s belongings, how was nobody bumping into Harry when everyone was getting off?
Harry had climbed up onto the luggage rack, hence why Draco keeps looking upwards.
Blaise shakes his head, smiling as he looks out the window at the darkness. Just then the small bag in the upper rack shifts. Malfoy’s eyes play over it.
On arrival at Hogwarts, Draco waits until everyone has disembarked and then zaps Harry, who then falls into the gangway.
Malfoy wheels, points his wand at the luggage rack. Something hits the floor with a THUMP. The Invisibility Cloak slips away and reveals Harry, paralyzed on the floor. Malfoy grins.
Much the same happens in the book, other than that it's Harry's ankle that gives the game away to Malfoy, not the shifting of the bag
Harry darted into the compartment, leapt on to Zabini’s temporarily empty seat and hoisted himself up into the luggage rack. It was fortunate that Goyle and Zabini were snarling at each other, drawing all eyes on to them, for Harry was quite sure his feet and ankles had been revealed as the Cloak had flapped around them; indeed, for one horrible moment he thought he saw Malfoy’s eyes follow his trainer as it whipped upwards out of sight;
and confirmed when Harry gets hit with some luggage
Harry was so busy staring at Malfoy he did not notice Goyle reaching up for his trunk; as he swung it down, it hit Harry hard on the side of the head. He let out an involuntary gasp of pain and Malfoy looked up at the luggage rack, frowning.
Malfoy then waited until the train was empty before petrifying Harry.
Without warning, Malfoy pointed his wand at Harry, who was instantly paralysed. As though in slow motion, he toppled out of the luggage rack and fell, with an agonising, floor-shaking crash, at Malfoy’s feet, the Invisibility Cloak trapped beneath him, his whole body revealed with his legs still curled absurdly into the cramped kneeling position. He couldn’t move a muscle; he could only gaze up at Malfoy, who smiled broadly.
‘I thought so,’ he said jubilantly. ‘I heard Goyle’s trunk hit you. And I thought I saw something white flash through the air after Zabini came back …’ His eyes lingered for a moment upon Harry’s trainers. ‘That was you blocking the door when Zabini came back in, I suppose?’