I can actually explain the 2 nuetral and one hot. The white wires could have been spliced in the triple gang box that feeds the receptacle, but instead it was hooked up through the receptacle for some reason... the triple gang controls 3 different light fixtures in the bathroom and the receptacle was not switched. Who knows why the original electrician wired it that way. I have had issues with the original plumbing as well, using a steel clip to hold the copper pipe to a stud. Well that corroded and sprung a leak that caused 20k damage to the downstairs unit. Anybody want to buy a condo?
Usually it's a passthrough (2 in, 2 out) and used to either GFCI a fan or something in the bathroom above the shower or just a plug in/out power on the line side. That's why I just asked for info when you mentioned three wires. Good luck!