how to retrieve history of local chat

[Lindal Kidd]

They have to have chat logging set in their Preferences.  If it's not set, they cannot retrieve the conversation.  If it is set, have them search their hard drive for a folder called chatlog. 

NOTE:  It is against the Terms of Service to share chat or IM logs with any other person, unless all parties to the conversation have given their permission.

[Lindal Kidd]

They have to have chat logging set in their Preferences.  If it's not set, they cannot retrieve the conversation.  If it is set, have them search their hard drive for a folder called chatlog. 

NOTE:  It is against the Terms of Service to share chat or IM logs with any other person, unless all parties to the conversation have given their permission.

[Rolig Loon]

Your own chat history is saved on your hard drive (if you have set your Preferences to do that).  If you open your AppData folder and look in the subfolder labeled Roaming and then the sub-sub folder called Second Life (or Firestorm or whatever your viewer is), you will see that there is a separate folder for each of your accounts.  I have one that says "Rolig Loon", and it has folders with IMs from anyone I ever talked with, plus a folder called Chat, where all my saved chat is.  If you haven't had your Preferences set to keep all those files, they won't be there, obviously.  If you have, though ..... that's what you have been looking for.

BTW, you should remember that it is against the TOS to share chat messages without the approval of people in them.