Is this a Word document? if so then what version Word are you using?
How did you delete the header and footer details? (What did you do)
Did you re-save the document with your changes before you emailed it? (he may have been able to undo your changes or the emailed doc was the unchanged version)
You could also check what info is saved within the 'Properties' of the document. (In word 2003, Properties is on File menu)