To help out, and ensure that those that didn't post letters can be easily searched for as well, I made a google doc with all the sign-ups on the AO3 side. This was done fast and quick. It does not contain any letter links. I have allowed commenting so that people can add links to their letters and any others that they know of. Don't abuse the commenting or I will turn it off.
I am a bit rushed right now, so the livejournal post will go up later.
Feel free to use this in whatever way you want for making any other documents to help participants.
Google Doc Link
EDIT: I have good news and bad news. So the underlying issue is still unknown. However, an AO3 database person was able to get me the CSV file and it was emailed to me. I will be sending it to the people that requested it for working on spreadsheets with the emails and offers removed. The bad news is that it did some pretty funky stuff to some of the tags.
ãƒ¬ãƒ»ãƒŸã‚¼ãƒ©ãƒ–ãƒ« å°‘å¥³ã‚³ã‚¼ãƒƒãƒˆ | Les MisÃ©rables: Shoujo Cosette
æ–‡è±ªã‚¹ãƒˆãƒ¬ã‚¤ãƒ‰ãƒƒã‚°ã‚¹ | Bungou Stray Dogs
It mostly seems to be fandoms with characters not used in English in the tag.