A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Usually the sync setup would be configured to perform two-sync and update the file with latest update data. Just check if the settings if there is an option to set one-way/two-way sync.
I doubt that you're be able to recover the changed data.
Delete and re-create partnership and check if it works.
Also check if the sync software is updated..
you may also repair/reinstall the sync software and check if it syncs correctly.