Hmm, not had the whole story here have we?
You state that they had not followed you, yet then state that the car had been parked for 2.5 hours?
From my experience with insurance claims, I would suggest that your vehicle was involved in an accident, it was driven somewhere other than your home address/where it is registered to, but the police found you near it and found you to be over the limit?
Would this be correct? If so, let's hope you get the book thrown at you for all relevant offences