The frustrating thing about Excel sheet tabs is that they cannot be easily restored using Ctrl+Z. Instead, you must restore a previous version of the Excel file, either from File History or using the versioning function of the cloud storage solution which you use to store the Excel file.
This is how you restore a previous version of the Excel file using File History:
Open Start and search File History. Open it.
Click Restore personal files.
Navigate to where your Excel file was located.
Select your Excel file, then click the green Restore button to restore it to its original location.