downloads in itunes missing

tried to copy a tv show to my ipod. it wouldn't work due to the download being hd. so i went to my account, "purchased" and redownloaded the episode in non hd format. it downloaded then disappeared. went to the hidden link under my account and it wasnt there. where could it have gone? this has been an ongoing problem and as usual apple is of no help. i keep getting passed from department to department. any help here would be appreciated. so frustrating i can hardly see straight. Thanks in advance.