Sorry to hear of your experience, but, sadly, if the person gifting you the cert didn't go to the airport to authorize it, the outcome was predictable.

Here is a link to the Consolidated How to Sponsor United e-Upgrades Thread. Section 2 of the first post deals with how it should be handled when you're unable to sponsor the upgrade online.

http://www.flyertalk.com/forum/showthread.php?t=258146