@Dreamy what he did was harassment. Legally they are not allowed to have you empty the entire contents of your bag in public, they need to take you to an office. He is to have another person with him, a shop attendant or another security guard and legally they are not to be alone with you.

You are allowed to ask for someone else to be in attendance. You are allowed to ask to see video footage of suspected theft.

I had this happen to me... I had my granny shopping trolley and this old lady had said "its her, she took my credit card". Out the front of the supermarket I was forced to empty out my entire trolley and handbag, show receipts from several stores in front of the food court. They showed no footage and I went up the chain. I can't say anything was done but it does help to feel heard

I am the kind to make noise though.