Is my thermostat stuck?

Several months ago, I thrashed my car on some windy roads. The car seemed to operating fine even under stressful conditions. On the way back, while in traffic, a car from oncoming traffic made an aggressive turn that forced us to brake hard to avoid t-boning him. After that I noticed the coolant temp skyrocketing. We limped it to the highway until it cooled down and did just fine - it handled 80mph (revving ~4k RPM) the whole return trip until we got off the highway where temps starting to skyrocket (I especially noticed this on on/off ramps). This continueed for a few days. The telltale sign that this was thermostat was that we lost the heater while the car was overheating. After a few days the problem just magically went away. I thrashed it on some steep hills with the A/C cranked to maximize stress and the coolant stayed cool; it was normal and I couldn t replicate the issue. Chalked it up the the thermostat that got stuck closed and got unstuck somehow.

However, now I think it s still, but open. Coolant temp is normal, but I noticed it takes longer for the car to warm up, and when I use the vent, even on the coldest setting, the air is noticeably warmer than ambient air.

Thoughts? Do you think my thermostat is stuck open?