Just because you think it's against to law to detain someone without them attempting to leave the store, doesn't make it true.
"Acts Constituting Shoplifting
Although we typically think of shoplifting as occurring only when an individual leaves a store with stolen items, the crime of shoplifting can be charged in a variety of circumstances. Since shoplifting involves not only the taking of items but also the “willful concealment” of them, it is possible to be charged with shoplifting even without leaving the store. Simply concealing goods will be enough to violate shoplifting laws as long as the perpetrator has the intention to deprive the owner of them permanently. For example, if a woman takes various make-up items while in a store and hides them in her backpack, a security guard may detain her for shoplifting even though she has not yet left the store."
" Detention of Shoplifters
Although our criminal laws typically prevent private citizens from holding others against their will, also known as false imprisonment, special exceptions have been carved out over the years for dealing with shoplifters. Since most stores do not employ police to watch for shoplifters, their owners are placed in a position of frequently needing to detain an alleged shoplifter until police can arrive. In order to do so, many states have enacted special statutes allowing stores and employees to detain shoplifters if certain requirements are met. Generally, someone suspected of shoplifting may be detained only if the store has “probable cause” to believe that a crime has occurred. Probable cause can be established through personal observations of the crime occurring, statements from customers, or actions recorded on surveillance video cameras. Mere suspicion that someone has been shoplifting is not sufficient."
Can you show me a link stating someone has to leave the store for probable cause? Or that employees can't detain a shoplifter by law?