Clock [Q] AT&T SGH-I317 4.4.2 OTA update broke mobile data on Straight Talk sim

Last night my AT&T branded SGH-I317 phone, which I've been using on Straight Talk for a long time now without problems, decided to do an OTA update. It looks like it put 4.4.2 Kit Kat Build number KOT49H.I317UCUCNE5 on there with Baseband version I317UCUCNE5. When I woke up and this update was complete, I had no mobile data. No amount of fiddling with my APN settings brings it back. Device status states that my service state is "In service" and my mobile network state is "Disconnected."

I'm really not sure what happened, but if I had to guess, the new radio firmware killed my sim unlock that I did a long time ago to get this phone to work on Straight Talk. I can still make calls though, so not sure.

Is this a known issue? I've been searching for hours and haven't come up with anything significant. Anybody have an idea how I can get mobile data back?