How do I find a missing home owner ?

I have found a house I want to buy. So I went to the tax office and they gave me a name (John Smith) and a po box address. I sent the letter offering to buy but got no response.

So I went back to the tax office to see what else John Smith owns and got a different street address. The folks at that address sat they never heard of John Smith.

He’s not in the local ph book.

A co-worker has a cop for a bro in law but the cop says he needs a b-day before he can help. I looked at a couple of web sites that promise they can find ANYONE but in the fine print they only promise to take your $10

Any suggestions on how to find John Smith ?

find out where the property taxes are being sent to good chance he lives in one of them.