Definitely requiring more information and detective work.  

One word: Pet Detective... 

I also put a water meter on our well to monitor use, it has been great for leak detection and therefore decreasing use.

This is where you detective skills come in.

It's hard to detect if you're not looking for it.  

Yes, landlording, in our age of specialization, rewards the jack of all trades  generalist, and a part of the job is detective work (along with handy person, cleaner, accountant, etc)...

@K. marie P. do I detect a hint of sarcasm?

I'd say if they won't just admit it's a pet, don't try to play detective.

And then he had me contact the seller personally once we found his number through some detective work, and the seller simply said he accepted another offer and that was that, I wished him a good day and hung up.

Remember detection limits for such are quite low.