If you have specific access logs to her WTB threads or her profile ("Who has viewed my profile?" etc) you would likely have something. But you would need a confirmation of the (dynamic) IP address of the seller in order to find him in the logs if the seller never posted anything here.
The mods dun have that level of access. I think only our 3 Admins can. Which is why we need the original WTS thread. It is a normal process to archive such threads especially if it is a police case... Which is why we only delete spam threads on buy/sell and nothing else.