It was really just the electrical socket in the closet that threw me. I don't think I've ever seen that, and I can't think why else anyone would want one there, but clever of them to take advantage of the situation--and you too!

That was one that came a little later on, after my dad was getting stumped trying to beat me on the technical measures.

I don't remember the specific product he used, but it was something very similar to this: https://www.amazon.com/Techbee-Countdown-Programmalbe-Electr...

The lockpicking was addressed with a more sophisticated lock, which was in turn met with a crowbar, which was in turn met with an increasing number of locks on the closet door, which was in turn met with me noticing the hinges were on the outside of this door and simply taking the door off the hinges without ever touching the locks.

I'm sure whoever buys my parents' house when they sell it in a few years will be a little curious about the one reinforced basement closet door with three pick-resistant 7-pin deadbolt locks, upgraded strike plates, and which is also the only closet door in the house with hinges on the inside, lol.

Did he have an outlet installed in the closet (or a closet built around an outlet) just to use that device, though?

At least the hinges should make it clear they were trying to keep someone out, not keep someone in...

The closet already had an outlet.