The webmaster says it can't be done. I'm sorry that your data is gone forever.
For your longer postings, I suggest that next time, you compose it first as a Word-file and just copy-and-paste it to the discussion board. It's the best, surest, and safest way to make postings on the Forum. Another way, of course, is to compose your longer postings on your Notepad first, then just copy-and-paste it on the board. Either way, you can refine your thoughts better and eliminate the possibility of loss of data.
Best of luck in your next posting!