OP, this sort of incident happens everywhere, all the time, to any customer. Shoplifting levels are through the roof nationally, every store has to be on the alert for any incident they can nab, and it is costing us, the consumers, and the retail industry, £4.2 billion a year, including crime prevention spending, and, at a broad estimate of two million shoplifting incidents a year, or 55,000 incidents per day, as Google's Gemini has just informed me. It is also adding £150.00 - £180.00 per annum to the costs of every household in the UK .
I have never stolen anything from a store, or from anyone else, in my life, but just to give you a few incidents that have happened to me. In Waitrose, alone in an aisle, I knelt down to see what brand of breakfast cereal I wanted to purchase, only for the officious guy in charge of alcoholic drinks to move straight to the top of the aisle, and glare at me in a very obvious way, arms akimbo, while I was selecting my products. There was no question but that I was being watched (I glared at him back when I was leaving).
I entered another Waitrose I didn't know last year, and, since I had no idea where anything was located, must have looked a bit doolally while I browsed around. I knelt down again to look at the different range of loaves on offer on one of the shelves. All of a sudden a member of staff rushed up to me, looking a bit panicked: "Excuse me, can we help you? What are you looking for?" Me. "Oh, I'm just looking to see what these loaves are. Ooh, this one is nice and warm. I'll have this, thanks", put in in my basket and grinned at him as I left. The expression on his face was a picture.
Another time, on a day out in Oxford Street - and this one was really unpleasant - I entered one of the big department stores, with a bag on me for a makeover I had booked at a hairdresser off one of the side streets. Somehow, I triggered off an alarm when I left, not having bought anything. Immediately, three guys emerged from different directions, seized my handbag, seized my makeover bag, seized my make-up bag, picked out and examined the various things in the bags, looking through an old receipt, everything. No communication with me, no eye contact. Finding nothing from the store, they let me go without a word.
Google's Gemini has also just informed me of the measures taken by the stores and government to combat this epidemic, "Project Pegasus" and the "Fusion Cells" or some such which I'll look at later, but until such time as these come into effect, all the friction and suspicion of the customer which a shopping experience involves these days will continue, and any one of us customers will continue to be pulled up in the way you've been.