That's true, if it was a GTB then they're meant to shut down when the motor overheats...but that isn't always reliable. What car were you running it in, and what was your gearing? You shouldn't have a problem finding a ratio that allows the system to run cool, so perhaps there was some binding in the drivetrain you'd missed?
Thinking about it, it might be worth hooking up another motor, if you have one, to your ESC just to be sure that it's still alive and well.
A temp gun is invaluable when it comes to gearing BL motors.
