It could have been clocked I suppose, I sold a Citroen AX about 10 years ago, I had it from new for 18 mths and it had done c24,000 miles. When I parted X ed it, the dealers were selling it with 9,000 on the clock. I had never had it serviced at a main dealer so no real service history.
My current car is a KA, again I have had it from new. It is just over 3 years old, done less than 20,000 miles and still doesn't have a full service history as I refuse to pay main dealer prices for a service! Not that I am selling it, I love it.
Just trying to say that just because it doesn't have a service history doesn't mean it isn't genuine.