I mean, right now I have a smart thermostat that tells me everything from how much energy I'm using to whether or not it has detected someone in the house.  

He also has a really cool thermal device to help detect air conditioning duct and insulation leakages.

Good luck detective...

The made up name she used with that most recent landlord - is that detectable somehow?

Walk by the property frequently and you may get lucky catch the owners or contractors there ... basically, good, old fashioned detective work, which could actually be fun and highly educational for future acquisition skills even if this one doesn't work out for you (most don't, but if you keep trying then some do). 

I would not take too much for granted about why people sell, nor would I take for granted that a person that has gone to a great deal of effort to shield their identities are going to be happy when you call and announce that your detective work has led you to them.

It doesn't detect water, just temperature changes from evaporation, overnight cooling, cold water in a warm room, etc.

If you have a genuinely hot lead pay a good private detective.

So right now they have basically looked over everything but not quite in details I suspect.During the inspection they detected some old pipes (polybutylene). 

The digital moisture gauge they used detected lots of moisture on top of the planks, and none in our carpeted rooms.