Yep. I had this same scenario in a four plex. the home run's first stop was in the bathroom light box with a switch loop. Someone (Maintainence) changed out the light and did not connect the neutral from the panel back into the bundle. The circuit still worked, current was returning thru pipes. (old construction, steel boxes, neutrals done up with buchanons without insulation)Ask about work done in the near past in any of the apartments!?
Checked an apt complex with 2 apts tenants report shocked in shower and at kitchen sink