After coming up with a somewhat lame story explaining how you tripped over one another to the nearby conductor who has come over to see what the commotion was about, and masterfully avoiding the questions about your owl, you stand back, both shocked as to what had just happened (this for sure will make you nervous next year!).
Maybe you were late? You weren't aware that the platform closes.
'It's gone', said Ron, sounding stunned. 'The train's left. what if Mum and Dad can't get back through to us? Have you got any Muggle money?'
Harry gave a hollow laugh. 'The Dursleys haven't given me pocket money for about six years.'
Ron pressed his ear to the cold barrier.
'Can't hear a thing,' he said tensely. 'What're we going to do? I don't know how long it'll take Mum and Dad to get back to us.'
They looked around. people were still watching them, mainly because of Hedwig's continuing screeches.
'I think we'd better go and wait by the car', said Harry. 'We're attracting too much atten-'
'Harry!' said Ron, his eyes gleaming. 'The car!'