So sorry, that really sucks.
My little guy, who is now six months old, stayed at the vet for 9 days.
He never tested positive for Parvo in 3 tests but my vet thinks it was Parvo.
He became ill a week after his third series of shots, you just never know and can't be to careful.
He is now healthy and happy, shows no signs of being sick. I feel extremely lucky!!!
Good Luck to you and RIP Cash