Unfairly Accused of Theft

I went with my sister to Pick n Pay Greenstone to buy toiletries. We bought face wash products and bio-oil. The next day we went to the gym with the same product to use. We decided to go back to buy vegetables. We used the entrance closest to the gym and the sensors at the door did not react when we went in. After purchasing the foods the next door sensors reacted and the bio oil reacted. We followed security orders and explained that we bought it yesterday. They took us to the office where they made us sit for an hour there was no camera evidence to prove we stole it because we were miles away from the toiletry section since we were buying vegetables. They told us to leave and come back with the slip which we left at home and they took our bio oil which we paid for. They treated us like ********* with no proof and the lady said people in this situation are guilty. The bald white head security rudely said people rarely come back with purchased products. I dont understand how a purchased product still has a tracking code since they said most purchased product have it so u can't come back with. Once they let us go they didn't give us an apologize they just brushed it away.