Just that you made blanket statements that may be correct for your state, but laws vary from state to state. It often depends on where yo live.
My daughter came by today, the one who is an asset protection manager and trains store security.
In California there is a Merchant Protection Act that governs what they can do. Her store developed a policy that is more restrictive on their employees so that they would come well within the law.
Her store does not routinely check receipts. However, she covers that scenario with her employees.
They have what they call five elements that need to be met in order to detain or make a citizen's arrest. They do so on a regular basis. Example one element can be selection. If they see someone walking around with an iPod they run the tapes to where the person entered the store to see if they came in with one.
In short they will apply probable cause.
In the example of the thread, they would not pursue a person who refused to show a receipt UNLESS they had met the other elements they need to detain someone. They may follow and take down a license plate and then review store tapes.
The law protects them if they act within the definition of probable cause. The company policy requires them to meet the five elements.
And Quick1, your comment about DU, after I left the thread, demonstrates a lot about your character, none of it good.