I offer my condolences to you on Archies passing. Sometimes, they just ...........go. I had the same thing happen to my little Max 9 years ago. He was fine in the Am and then poof ! Gone in an instant, with no warning. The cause can be maybe found out by doing a necropsy, but the body has to have been refrigerated (not frozen) almost immediately and those are NOT cheap. Archie no doubt knew how much you loved him, so you can take heart to that. Remember the good times you had with him, and forget the bites and screaming over the years, it will hurt less with time.
I donate to Cornell Univ's vet program twice a year and I make it in the name of all the ParrotForums babys that have passed in the interim. The donation is directed to be used for Parrot related studies and programs. Archies's name will be included.