So your single use alarm still didn’t go off on January 3rd like Apple said it would? Well you can fix this by editing your alarm once and then saving it. Just change the time or name and save. You may then re-edit to your previous settings. Apparently a non-repeating alarm saved previously will may not go off on some iPhones, as was the case with mine, a 3GS running 4.2.1 firmware.
Just tested the re-saved alarms and all went off without a hitch.