Apple came through
Dear Steven,
Thank you for contacting iTunes Music Store Customer Service.
We apologize for the inconvenience you have experienced with this title. We have regranted your ability to download it again. To download again, verify that you have an active network connection, open iTunes 4, and select Check for Purchased Music from the Advanced menu. Should you have an issue with the new download, please reply to this email with the follow-up in the subject line or the message body.
Sincerely,
The iTunes Music Store Team
Of course, I’ll wait until I get home to try to download the song, but they get points for getting back to me quickly.