Well you got the answer in your own question bud, sorry but no way to recover it AFAIK, maybe the more technical people can help you with it
NSA must have a copy anyway. I don't think the odds are that they will share it..
If you have not previously set it to save conversations for longer than a month, then it won't have. Always save important conversations in logs for later retrieval.
I wouldn't suggest Skype for any sort of business deals, though that is just me. The program is extremely insecure and can cause you problems should you not protect yourself adequately.
I know, Skype is a really stupid software. I wasn't using it a few months ago, but lately I had to. The only thing I see good with it, it is very simple and easy to use. Well, if I can't even check what happened a month ago (I thought that was why people use these things so that they won't forget. Now Skype forgets things faster than I do..) it isn't worth it.
Do you know any safe alternatives? Does Google Hangouts store messages older than a year?