Did you close/save the workbook?
If no, then you could close without saving. You'll lose your changes, but that
may not be as bad????
Do you have a backup version of the workbook -- maybe your IT staff made a
backup, maybe you sent a copy to a coworker (in your Sent folder???).
You may be able to get it back from there.
If you don't have a backup and you've already saved, then you're out of luck.