A walk-in sale is a sale not associated with a customer account. It was a sale processed by clicking on Walk-In Sale.
We highly recommend creating a default "Walk-In" Customer account for each of your locations to avoid this scenario from occurring. For more information on how to do so, please visit this article.
Since the sale is not associated with a customer account, you'll need to reach out to our Support Team via chat or email to process the refund.
When reaching out to our Support Team, please share the:
Order number
Name of the product(s) to be refunded