Seasons of Alzheimer's

In the afternoon, we went to the Salvation Army warehouse to help wrap gifts for children in need. Mom and I enjoyed our afternoon. I put Mom's hand in place to hold the paper, and I would hurry to get the tape on before she lost grip.
Mom repeatedly asked, "Who are the presents for?"
I repeatedly said, "They are for children and families in need."
Mom was happy all over again.
On the way home, I decided to stop at the health food store. I only needed a couple of items, and there was a parking space close to the store. Mom said she was too tired to go in and wanted to wait in the car. I agreed, and it would be quicker for me to go in alone. She was buckled in her seatbelt and hadn't yet remembered how to unbuckle it. I was confident Mom would be fine. I locked her in the car and told her I would be back in five minutes.
I grabbed the items I needed, peeked out the window, saw Mom in the car, and proceeded to the checkout. There was one customer ahead of me. Checkout went fast, and I rushed out to the car. Mom was gone! I panicked like never before. I wanted to scream. My mind raced. What should I do? Should I call the police? I cried, "Where did Mom go?"