I picked the car up from the repair shop today after they replaced the thermostat and a lower radiator hose along with a temperature sensor. I'm assuming they flushed the coolant since they charged me $20 for it.
On my drive home I took it on the highway and had sustained speeds of over 40 mph with the ambient temperature at 30 degrees F. Unfortunately, the temperature gauge again started to drop and finally rested just above the blue and the cabin heat became non-existant. The coolant light never came on but I wasn't at those sustained higher speeds for very long and it wasn't terribly cold relative to the other instances this occurred. So, it could very well still be there (I just wasn't able to tell given the limited sample time).
I'm taking the car back in on Wednesday (Feb. 6 - 2 days from now) because I have some scheduling conflicts. They want to take the car on an extended test drive and run some more diagnostics. I'll report back again and thanks for all of your responses, they have been nothing short of awesome.