Bava Kamma 63: Thievery vs. A Claim of Thievery

What happens when a person comes to collect the item that another US safeguarding, and the guardian says - it was lost (or stolen). The guardian can be asked to swear to the veracity of his claim. But then other means (witnesses) attest to the fact that that claim was a lie. What kind of compensation does he have to pay the owner? Also, an investigation into baraitot that teach the handling of a thief - if he's found or not. And running through the text, the ongoing dispute whether the case is a thief or a claim of theft. And how do the biblical verses teach the details of the false claim?