It is very easy, actually. Remember, 3rd world countries often don't have a lot of building regulations, permits, etc. Data isn't crossed. Payments are often made in cash. He probably didn't do taxes, social securities or any of that sort of transaction that creates records. The local people either only knew the house as "the big house on the hill" or as the place you really don't talk much about.
I have seen this again and again here with drug bosses living in gorgeous houses that no official knew about. A friend was trying to sell a large, beautiful ocean front house. He gave up because his conscience wouldn't allow him to take the deals that were offered: fake names, no questions asked cash, not reporting full value, illegal off-shore money and so on. This was in Rio, not even a village. If you go to more remote villages (and if you consider bad roads and bad data infrastructure, 100 miles can be remote), it is even easier.