Customer wanted to get refund after I checked out her only 1 item

It was at 10:20pm, and I got an easy 1 item order offer so I accepted it. Went to the store and it’s sold out. The app gave me 3 subs options but none were in stock. It prompted me to the next page to contact the customer.

Remind you it’s 10:30pm and I wanted to go home for the day. I saw there’s similar item, but $10 more than the original item so I scanned it as a sub and the app went through. I went to check out line and scanned my barcode, that’s the time I saw a customer messaged me asking for other options. I told her that there’s none left. She told me she wanted a refund. I told her that I cannot do it on my end. The app told me to deliver the item. She asked if I already checked out which I did.

After I checked out, I waited couple minutes in store and asked her to see if she could cancel the order on her end before I delivered it. No response. So I went ahead and delivered the order.

Did I do something wrong? Now, I am worried that she may give me a bad review. What could I do if it happens next time?

Thank you