It's behind the refrigerator, or in another place you haven't looked yet.
When was your house built / electrical redone? That might help narrow it down.
Is there an outlet next to the breaker panel? Is it a GFI? Is it tripped?
I was just in a hotel, the outlet in the bathroom wouldn't work. Hit reset on the GFI, no go. Had to hit "test", which popped out the button, then hit reset, then the outlet worked. Try that.
Failing that - Amazon does sell circuit tracers