So I did. And it was the same girl.
"Have you got a hard-sleeper for Beijing tomorrow?" I asked.
"Only soft-sleeper," she said. The price was too much.
"Can I have it for the price of a hard-sleeper?" I asked sarcastically, but not without hope.
"Why?" She wasn't amused.
"Because the other day when you probably had some hard-sleeper tickets you told me to come back the night before travel. And now you say they have all been sold."
"Well since then many people have bought tickets."
So she did have some before, but my luck wasn't running.
"What about the other train?" I tried again; there were two trains to Beijing.
"Only one ticket left. Soft-sleeper only!"
"Can I have it at Chinese price?" She began to soften at my persistence.
"Because I'm a student," this was sometimes a magic word in China.
She laughed: "Show me."
I showed her the plastic card that was readily available in Hong Kong.
"Can you speak Chinese?"
"No, but I'm learning," I said.
She refused, but at least I was getting through to her on a human level.