How to Get a Replacement CD
Q. My copy of Office was stolen. How do I get a replacement CD?
A. To obtain replacement CD-ROMs or manuals if your copy of Office is lost, stolen, or broken, contact the Microsoft Replacement and Supplemental Parts Department at (800) 360-7561.

When you call for a replacement CD, you may be asked to fax a copy of the store receipt to the Microsoft Replacement and Supplemental Parts Department.

Note: If your copy of Office was preinstalled in a computer or distributed by an Original Equipment Manufacturer (OEM), you must contact the OEM for a replacement. If you acquired a copy of Office through the Microsoft Open or Select Volume Licensing programs, contact the Microsoft Worldwide Fulfillment Office at (800) 248-0655.
Taken from the MS Partners newsletter.

I wonder how they could verify this. It's good to know that MS honors their product in this way. I think it is a good way to retain customers.