Hi Antheia,
There is a history for PM chat, unless it was recently turned off. I have accessed my own PM chat history in the past as well.
It doesn't keep the history forever though, as it does get deleted. I am just not sure how long it takes for that to happen. If you had a private chat yesterday, it should probably still be there. So you may still be in luck.
There are 2 ways that I know of on how to access it:
1. You could just start another private chat with the same person again. Once the private chat window opens betwen you two, you should be able to go back into that windows history and copy it. Just highlight the text with your mouse and use "CTRL C" or right click your mouse to copy it.
2. Every private chat has a unique ID number between 2 people. If you go back into your browser history, you may be able to find that ID number. The link will look something similar to this:
Code:
http://www.spiritualforums.com/vb/chat/private.php?uid=123456789
If you find the UID for 'your' chat, you can paste it into a web browser and then your private chat window will open so you can copy it.
Good luck! I hope that helps and was clear enough?