Silly, you have to ASK for the refund. At the station.
Was that in 1991? The year most countries in Europe devalued their currencies, and Soros shorted the pound and mad a billion dollars, back when a billion was a meaningful sum? If so, yes, I do remember it. I don't think the DM participated in that, though I'd have to look it up.
I"m sure you know you should NEVER change money at an airport or train station.