I'm so sorry to hear about your puppy. I would add that I recommend distemper/parvo vaccinations every 3-4 weeks starting at 6-8 weeks of age, and ending at 3 months of age in most breeds, and adding an additional vaccine at 4 months of age in breeds that are very susceptible to parvo, such as Rottweilers and pitbulls. 80 days of age is about 11 weeks, so the last vaccine may not have caused protective immunity. However I have also seen parvo in puppies that were completely vaccinated--as Dr. Humphries states, vaccines are our best way to avoid infectious disease, but no vaccine is 100% effective. Although an autopsy would be the best way to find out why your puppy died, if you have any samples of the bloody stool left in the yard, you could take it to your veterinarian for a parvo test, since the virus is passed in the stool and is very hardy and can live for up to a year in the environment.
Kimberly Coyner, DVM DACVD
Sounds like she did have adequate vaccination protection, so may not be Parvo. However to answer your question, yes Parvo can be fatal in a matter of days or even hours.
As for what else this could have been - would be pure speculation on our part.
I am so sorry this happened to your very young and loved dog. Talk with your veterinarian about sanitizing your environment well before bringing in another pup. And just as you did before, get all those shots! Remember, vaccination is our best attempt to prevent animals (and humans) from getting disease. BUT NO vaccine is 100% effective. So much depends on chemistry, virology, bacteriology, immunity, dose of infectious agent etc. Science is still a mystery.