Hey Paula, while I definitely agree that it would be nice to get a non-bgg way to log in, it seems like you have to be pretty intentional to get stuck...
1. delete the email from jeffy jeff with the link. Most people forward geekmail to email, right?
2. delete / prevent cookies in your browser
3. delete the browser history containing the login link
I'm PRETTY sure that the 7% at this point are non-submitters (or even just blank wantlist submitters) or people who plain old forgot that this was going on tonight. I doubt that there are any people who are hosed in the last 3 hours before the math trade ends because they basically MADE themselves unable to log in w/out depending on bgg. When I have a link that I need, keeping it in my geekmail is probably the LAST thing that I would do (as opposed to, say, a bookmark, normal email, browser history, etc... I understand your concern about not getting the one trade that you wanted, but I also want to assure you that the majority of people not submitting are laming out rather than being PREVENTED...