How old were the posts? If you REALLY need them your best bet is to use Google. If you Google your old forum name and only look at this site, you should be able to come up with some older posts of yours. You can click the links but those might not work. If you find a link that does not work then you should try going to the cached version. It's the green arrow to the right of the link. These will not be here forever though.
Your search should be something like this..
Ursula site:community.quickbase.com
That will search for your current name only on this website. Just replace Ursula with your old name and you can put quotes around your name as well, sometimes that helps.
I know this isn't a perfect answer but hopefully it helps you find some old posts.