I wouldn't worry that much about the thermo - even with it, if I didn't have a blockoff I'd often hover at 150-160 on the highway in cold weather. I'd guess your on-track temps probably spiked up to 200 or more but you didn't notice. It would be difficult to cool this car's oil enough to maintain 180 in a track session, even in the bitter cold you've had up in that area lately
And yeah, by default the thermo plate is fully open in all senses. At temp it should close off the bypass and force oil through the cooler only (not the bypass).