It's most likely gone, BUT it's possible a file recovery service could get it, but those can be VERY expensive. What do you need it for? You could also try a computer utilities program, like PC Tools, or Norton Utilities, and have the BB connected to the computer in Mass Storage Mode, but it's unlikely you'd be able to find and restore the text.
Get a free account at www.dexrex.com and as long as you keep the app on the phone, all your text messages, will be backed up. Then barring their servers going down, you will have a backup of all your txt that you can view online.
Posted from my CrackBerry at wapforums.crackberry.com