Dear Mike Engineer,
Good day to you!
I hope you are well. Thank you for reaching out to our Microsoft Community Forum. We will be happy to help you.
I understand your concern—losing important documents can be very frustrating. Based on your description, it appears that your colleague worked on the same file without saving it, which resulted in the loss of your previous data. If you could share more information about the file location, it would help us provide more specific guidance.
Is the file stored on a local device or in cloud storage, such as OneDrive?
Once you provide this information, I will do my best to assist you further.
In the meantime, you may check the Manage Workbook section in your Excel file by following these steps: Open excel file > click on File > Click on Info > click On Manage Workbook > Select Recover Unsaved Workbooks.
We need to first clarify the information before we can determine the subsequent troubleshooting plan, so we are sorry that we cannot directly provide a solution.
Thank you for your understanding. Your cooperation and contributions are greatly appreciated.
Kind Regards,
Nahid Sultan