Believe it or not, the first thing to do is to check all the tire pressures to make certain they are within spec and equal. A low pressure tire will make more revolutions/mile than the other properly inflated tires, and can confuse the ESC/ABS module into thinking there is a problem with one of the wheel speeds.
The most common hardware failure that causes this error is a wheel speed sensor (ABS). They are exposed to some pretty harsh conditions, and can have broken wires, a rusty tone wheel, or a failing sensor winding. However, this should have been detected by the Service Technician. - although if the sensor winding is failing, the error may be intermittent. It is possible the ESC/ABS module itself has a problem, but I would address the easier more common causes first.
With the proper OEM "VAG" type scanner, there should be codes that can be scanned to reveal the details of the ESC fault. If the light comes back on, leave the battery connected to preserve the code. It is not particularly hazardous to drive the vehicle in this condition, and no damage will be done. However, note that your ABS system may or may not be functioning while the fault is active.
Have you tried holding the traction control button in for several seconds with the car idling? This might reset the condition.