I'm surprised the electrician couldn't tell you where to look. The breaker box is normally labeled.
First, think outlets. Take an outlet tester (or just a nightlight) and plug it into all the outlets in your home starting with the outside ones which most people ignore. Remember that some outlets are controlled by wall switches and might be off.
Next, think seasonal equipment. You will likely not notice if the heater is not working after you open the breaker.