Chief,
The Scenery Library works in layers, with the pieces at the top of the list getting the highest priority in terms of display. The sim can display some unusual visuals when things are out of order. This link below has a good explanation for how the scenery library works, and in what order everything should be in, generally. I've used it as a reference in the past when troubleshooting my own system (raised/sunken taxiways comes to mind). It says it's for FSX, but P3D works the same way.
http://c-aviation.net/fsx-scenery-library-order-orbx-global/
Have you tried going into the Scenery library and disabling all of the other addon scenery you have except the affected airports? If the terminals show up, then one of your other addons might be the culprit and you may be able to narrow it down from there. It wasn't clear in your other thread whether your KATL and KORD are addons or not, but that might help with troubleshooting the problem.
I did a quick Google search on "P3D missing buildings" and got a number of hits on some of the other forums (including Avsim and a few scenery devs), but didn't immediately see any common solutions. Looked like a number of folks had similar issues at one time or another, though. You might find something if you look around.
Sorry I'm not able to be more helpful. Hope you can get it sorted quickly.