I had items on my shopping list that I didn't buy but that were scanned.

Today I experienced a strange situation. While I was shopping and checking my receipt, I noticed an item that I neither recognized nor had purchased, nor had accidentally put in my shopping cart. I went to the checkout and explained the incident to the cashier and was able to prove that the item was not in my shopping cart. At first, she refused to help me, but when I persisted, as I was not aware of any wrongdoing and could prove the contents of my shopping cart, she finally had to pay me the amount of €1.79. Later, when I got home, I became aware of the whole situation and realized that a woman had been standing very close to me and my friend the whole time. It was getting very uncomfortable, but I didn't dare say anything. This woman was with us the entire way through the store and eventually behind us at the checkout. Her behavior was most noticeable after we finished shopping. I stood alone at the edge, and this woman parked her shopping cart right next to mine, even though there was still space elsewhere. I turned away and checked my receipt because I was now very uncomfortable being so close to her. I stood there with my back to my cart for a while. Then she walked away very quickly. I suspect she first put an item in, which I paid for, and then took it out again. Has this situation ever happened to anyone else? What do you think? Can anyone tell me anything about it?