Deamer2k5
I think
pcr is on the right track unfortunately. Your
Vin/Chassis number will confirm whether your Civic is a '07' or '08' model. The '08' models have the modified parking brake. That is my understanding but I feel this may be irrelevant. Whether you have an '07' or '08' model, if the handbrake was still applied upon your return to the car, it appears that you may have suffered the 'cooling disc' syndrome. You are not alone.
"The letter" concerned parking brakes that self released which is not the case with your Civic.
If you care to go back some way on this thread you will find instances similar to yourself. In addition it appears you did not leave the car in gear.
I am sorry I cannot offer you the excuse you are perhaps seeking. I only wish I could be more helpful.