This housed a live 20a receptacle when I discovered it. I quickly traced the power and what I discovered really made me angry my parents had not had their home inspected before buying it.

Don't you just love it when you find stuff like this! I am also not too sure about those home inspections (HI). My son bought a house last year and there was a ton of violations and mistakes. Now granted a lot of the violations were open splices and some of them were behind the dry wall. The HI could not have seen those problems, but when he and I were walking around the house, and he looked into a sub panel and the neutrals and grounds were tied to together, he thought that it was OK. I politely told him that it was a violation of the NEC.

Donavan:

Welcome to ECN!!

Let's talk about the 'box & outlet' a little.

Was there a WP cover and receptacle in the box?

As it's not really clear, was the wiring that fed this box within the EMT?

IF the answers to the above are "Yes", and the receptacle had correct polarity and GFI (if applicable), then it's very doubtful that a HI would have flagged it.

I'm assuming that the wiring you discovered was connected to the zip cord you have in another thread.