Under English common law (and thus most American law), that is precisely the proper owner. The owner hid the treasure and presumably forgot about it or died before he could alert his family to its whereabouts. It seems most equitable that the money should belong to his heirs.
The contractor had no claim either.
Again, under the common law, the treasure trove belongs to the finder, not the property owner. Some states have rejected this, but I believe it's still the majority view. Don't know the Ohio view. Either way, it's an interesting set of facts.
What if there were multiple owners or multiple tenants? What if the hidden money was originally stolen from an enterprise that no longer exists and has no successors or assigns? Or if it is the proceeds from bootlegging or other criminal activities?
It's very difficult to prove that the money was put there by any specific person and whether the concealer, and therefore his estate, had a right to it.
There is also a common law tradition regarding possession.
the treasure trove belongs to the finder, not the property owner
Inside one's own home?
If we invited a couple over for dinner and the wife noticed that a yardsale end table buried under a bunch of tarps and tools in my garage was, unbeknownst to me, an incredibly rare antique that could fetch hundreds of thousands of dollars - could she just grab up the end table, run out to the driveway, and put it in her trunk and drive away with it?
That seems highly suspect.
I'm not sure this would belong to the finder under any theory of law. In England a treasure trove only went to the finders if it was clearly abandoned, otherwise it went to the king. This property wasn't really abandoned (so you're correct that it should probably go to the estate of the person who originally hid it), but between the finder and the homeowner, I think the clear trend in America is to award it to the homeowner since the contractor was simply an agent of the homeowner.