Once you delete a transaction like an invoice, there's no way to retrieve it. Instead, you can utilize the Audit log to get the information of the deleted invoice and recreate it. You can customize the Filter tool to narrow down the data.
Here's how:
Go to the Gear icon.
Choose Audit Log.
From the Filter drop-down, choose the appropriate User, Date, and Events filter.
Click Apply.
Locate the deleted transaction.
Use the browser search.
Press Ctrl + F on your keyboard.
Enter a keyword about the deleted invoice.
Under the History column, click View.
All the information needed for the transaction can be found under the EVENT column.
For more information about using the search tools in QuickBooks Online, you can check out these articles: