Chris is a contractor and is building a new home. He goes to a local hardware store and loads many items into his cart. When he is ready, he wheels his cart to the cashier who begins to scan the items. Chris doesn't notice that the cashier did not scan one of the items in the cart. When he leaves the store, the security guard notices that Chris is leaving with an item he didn't pay for and stops Chris. 

In the scenario above a mistake of law or a mistake of fact?  What is the likelihood that Chris will be found guilty of theft?Explain