As an update, I opened the board and used a multimeter across the contacts of each of the 4 dead switches. My multimeter beeps when each of the 4 keys are pressed, so the switches are fine. The signal just isn't getting to the controller. Can traces go bad on their own without any trauma to the board?
It has to either be corrupt firmware, a scratched trace, connection to MCU gone, or Chip fragged.
It is certainly possible for the solder joint on the controller that connects to the trace to fail. There is very little contact there to begin with. Any condition such as temperature/humidty change or a possible vibration from moving or even static shock could have possibly broken it loose. This time of year I would usually assume it was something caused by static shock. Possibly corrupting the firmware, possibly fying the processor.
Are you absolutely certain you didn't do anything recently that could have scratched a trace? Did you have a stabilizer pop loose and try to get it back in? Random, but I scratched a trace doing that once and didn't put two and two together even after several days of troubleshooting.
If it was my board, I would start by re-flashing the firmware. If that doesn't work, you could try to find the pin on the chip that controls that column. That's a bit hard for me to do with my multimeter b/c it sucks... ha. So I, personally, would reflow the pins on the MCU. Add flux to all of the pins on the chip and use a flat tip iron to hold on heat for a few seconds across several pins at once while keeping a small bit of pressure on the MCU with some tweezers or such.