Also, there are several customer reports QBO offers so you can have a summary of their transactions. To open one, please refer to the steps below:
Go to the Reports menu.
Scroll down to Sales and customers. From there, choose the report you want to open.
You can also filter the details by clicking the Customise button.
That's it! You'll now be able to get those deleted customers and invoices. Feel free to come back here again if you have other concerns about this or any QuickBooks-related questions. I'm here if you need further assistance. Have a good one.