I appreciate you for getting back to us, @nancyl.

You can resort to your customers' list to get it back to the original or its default order in QuickBooks. Also, I've checked that the QuickBooks version that my colleague used isn't QuickBooks Enterprise Solutions 16.0. I'll show you how:

1. Click on the Customer menu and choose Customer Center.
2. Go to View at the top left of QuickBooks and select Re-sort List.
3. Select OK to confirm the action.

Here's an article for more detailed steps and information: Re-sort Lists.

However, if the issue persists, I recommend contacting our QuickBooks Support Team. They can further investigate this matter and can create a ticket number.

Here's how:

1. Click on the Help icon at the top menu bar to select QuickBooks Desktop Help F1.
2. In the Have a Question window, scroll down to choose the Contact us link.
3. This will display the Contact Us screen.
4. Go to the Tell us more about your question section to enter the issue or topic in the field box.
5. Click the Start a message button.

You can also run the repair tool. This tool can help fix any possible data damage and refresh the QuickBooks program: Repair your QuickBooks Desktop for Windows.

Please know that you're always welcome to post if you have any other questions related in QuickBooks. I'll be around to help. Have a good one.