2001 3.8l V6 Temperature gauge scare?

2001 3.8l V6 Mustang


I was making my way home from the city, stopped to fuel up. When I left the gas station, my car almost instantly started to sound like a diesel truck. I look at my temperature gauge, and it's pinned in the red. My father (I was not driving the car at the time) turned on the heat full blast. It blew hot, and the gauge slowly made it's way back to dead center. My car has never over heated before in my ownership, although I've owned it for less than a year. It's never been a hair over smack dab in the middle of the gauge. My car was not idling long, fluid levels are all fine. What could have caused this scare? I'm hoping it just 'stuck' and a new thermostat could be key.

Any helpful insight appreciated.