Viewing Somebody's Skype Messages (with their un and pass)

[da teacha]

So yesterday I logged into somebody else's Skype account, and by chance, there was a whole conversation log there with one of the contacts.

I was under the impression that Skype saves messages locally, so I'm quite confused as to how an earth it would be possible to see these messages.

Is there any way I can exploit this in the future? I have the username and password, but usually, there's no information around....