The best I can find out for you is that it is gone. I thought their was a way on Intuity, but their is not. Intuity does have a feature with it that if you delete a message by mistake and you did not hang up yet, you can hit *U and it would undelete the message for you.
Sorry. I know that's not what you wanted to hear. If you find any mistakes, please consider that they are there for a purpose. And everyone needs a purpose.
Hope this helps, Mikey.