It seems to be a little different (and easier) for some reason to get an SWU coded properly for international flights. They just have to active the priority waitlist and enter the SWU number into the PNR, and if it hasn't cleared by checkin then it should be automatically passed to the airport standby gate upgrade list. At this point, according to the SWU terms and Delta internal procedures, you are ahead of any non-rev upgrades or other operational upgrades.
In fact, from my experience if op-ups are needed the people on the SWU waitlist are usually given the upgrade without using the SWU.
As mentioned, you got hosed badly and I hope you report this.