Personally, I don't think this is a big issue.
Yes, they have ****ed up, but nobody died!
You have a three year 60k warranty, and, when the book is stamped, you have proof that you have had the car serviced as per manufacturers, so no warranty issues.
These engines, basically are very sound, so it won't cause you any long term issues either.
The book will be stamped, so any future purchasers,or trade ins will be happy it has a full Alfa service history.
How many of us can be 100% certain any of the services we have had done are completely by the book.
Years ago a mate of mine got a job as a garage apprentice,and was told to change the oil on a first service on a nice new Saab turbo.
Dropped the oil, changed the filter, went for a tea break, came back, ran the car to check all was ok, and the car stopped.__Yes, he forgot to put the new oil in!
They let it sit all day, filled it with oil. It started and the customer took it away blissfully unaware.
You never know, perhaps it's a good thing they never did the service
I would do a oil and filter change myself, and rest happy. Nothing else major is done in the first service anyway.
The oil and filter change, will also probably be cheaper than the AA visit, and you can put the problem to bed and enjoy your car.
Going down the AA route, could prove you right, but it won't really get you anywhere, and you will have had loads of sleepless nights worrying about it, and your cholesterol levels will be a few points higher for nothing!