Read the passage below and answer the question!
 

Bad Experience

    I had a bad experience when I did shopping. Actually, it was not my fault. It was the shop assistant's fault. However, the security officer of the shop really embarrassed me. He accused me of stealing a pair of the blue jeans.

    Here how it happened. One Saturday afternoon I went to fashion shop with my friends. I wanted to buy a pair of blue jeans. I got one. I took them to the cashier and paid for them. Then, my friends and I left the shop.

    There was a censor clip on every piece of article. The shop assistant was careless. She forgot to take it off. Therefore, when I left the shop, the detector beeped. The security officer shouted at me, "Hey you! Stop!" He caught me. Everyone in the shop looked at me. Then, he took me to the manager's room. How embarrassing?

    Shortly, the soap-assistant and the security officer said they were sorry about what had happened. The manager of the shop did too. They knew it was not my fault.

    Finally, the manager asked me to take one piece of clothing article free. I took an extravagant gown. You know the price? It was Rp. 102.900,00!

Why did the writer say that was not her fault?