Well,,have the folks who have house for sale,,,do they still live in local area???
Did they move and buy another home??
They Amy have kept same phone number.
Utilities folks,,,you might go there and get info.
Courthouse deeds may show if the property is truly in the owner's name- sometimes it is not.
License plate numbers of visitors to house,,,if the owner you might find out.
Talk to neighbors,,they may have info.
Any stores close by,,they might know some thing.
Property tax records are public,, might try your trustees office.
Any local law dogs you can talk to.
Local post office might have info.