Nuked

I'm interested to see how my car trouble plays out.  I had it towed to the mechanic for fear of it overheating, which is difficult to judge on account of the temperature gauge not working.  The mechanic got ahold of me today and it didn't sound good.

The Mechanic:  "We drove it all over the place and couldnt get it to overheat."

Me:  "I had it towed there to not run the car, I just wanted you to check the heater core."

The Mechanic:  ".........oh.  I'll call you tomorrow..."

Either they nuked my engine or it wasn't ever broken.