Return DVR with no serial number

I took all my Directv eqipment for my cancelled service to UPS and they would not accept my DVR because there was no serial number on the bottom. This equipment has not been moved since it was installed and I cannot say whether there was a serial number on the bottom since I did not inspect it. No one in this house has removed the serial number. I have now been on hold for 61 minutes. Anyone have any suggestions?