Previous accident history?

Morning all, after a bit of advice from the collective knowledge on this forum please.

I have noticed the last couple of months that my rear NS wheel arch paint has started to 'bubble' (only way I can describe it) and now has some rust spots coming through. I asked Audi to have a look to see if it would be covered under the anti-corrosion warranty and after investigation they said it wouldn't as the paintwork had previously been repaired, likely as a result of an accident. There is also a very small patch of the bubbling paintwork on the rear OS wheel arch, leading me to wonder what sort of accident this was?

I bought the car just under 2 years ago through the Audi Approved Used from a dealership in Yorkshire, since then it has had all servicing done at Audi (as they gave me 2 yr free). They didn't state any sort of accident history when I purchased the vehicle (they may not have know themselves of course). My question is, do I have a leg to stand on if I go back to the original dealer to see if they will square it away, or assist in some way?

Thanks in advance for any assistance

Thanks guys, from what you're saying so far its pretty much as I figured. The repair wasn't done in the Audi network, they told me that after the investigation on Friday, so may well have been done by a 'backstreet' place. They knew it had been repaired as the paint thickness was wrong?
Figure its still worth a try at the dealers I purchased it from otherwise I'll be shelling out myself as it'll only get worse.