Sorry for the death. Problem with reptiles is they are very good at hiding an illness. They do this since in the wild, a sick animal is food. So usually by the time you see signs its already too late. That's why you want to keep your husbandry spot on and keep up with it.

And not to pry into it but did the folds disappear when you got to the vet or something? And my advice is find a vet before you need one. They are worth their weight in gold. My vet has saved Allison when she somehow ingested some Provent-A-Mite and has treated my beardie and Colombian BCi over the years.

Seems weird your boa ate with no regurgitation and then just died. Usually a sick snake wont eat. Maybe some chemical poisoning? I mean its all guessing unless you have a necropsy done.