A friend of mine got a new dishwasher because her old one stopped working. When the installer checked the circuit after it was installed, he found it was off. There is a switch in her kitchen she never knew what it did, and it turned out that it is connected to the dishwasher and got switched off.
Almost the same embarrasing problem I once had. I lived with my now-ex and we bought a dishwasher. Problem was that sometimes the circuit breaker tripped when we used it. When the electrician came, he found out that even when the dishwasher was off, there was around 7-8A used on this circuit. It turned out that the socket in the garage was on the same circuit (of course not marked in the breaker box), which my engine heater and compartment heater was plugged into...
Stig