Weird... When you listed yourself in Travelnet, did you list for First Class? What was the standby list screen at the gate showing? If there were seats available, you should have got them. I've been flying Delta for over nine years and I've always got a First Class seat when I listed for one and it was available.

Correction: I noticed you traveled before inventory cutover so you would have been traveling using the NWA non-rev listing and procedures. I'm not familiar with how that works.