Welcome to the forum, servicing for vag cars is 20k or 2 years which ever comes first, as they use long life oil I believe. Therefore it has missed a service by 6 months and 1000 miles. As a general rule this should be ok but I have to agree and question whether it fits into Audi approved used criteria.
It sounds to me like it was an ex lease car or company car, or something like that. What did the dealer say when you point it out?
Cheers
Steve