For simplicity’s sake, we will deal with this as if it were a theoretical case occurring in Israel and avoid factors that might arise elsewhere due to local considerations.
The gemara[1] discusses a situation in which one finds an object in an ancient wall and there are signs that it has been there since before the Israelites conquered the land. It says that the finder (even if he is not the property-owner) can keep the object. Tosafot[2] asks why the property (chatzer) did not acquire the object on behalf of its owner, even in the absence of his knowledge of the object’s existence.[3] Tosafot answers that a chatzer acquires objects for its owner only when it is expected that he will eventually find them.
In our case, it could very well be that the homeowner would never have found the object. Therefore, the money was un-owned (see discussion below), allowing the contractor to acquire it upon finding it. This basic idea is accepted as the halacha in the Shulchan Aruch.[4] There are two possible explanations for this law. The S’ma[5] says that a chatzer acquires only objects of hefker (ownerless status), but not lost objects, even when the objects’ owner gave up hope of recovering them. The Netivot HaMishpat[6] says that it depends entirely on whether the property-owner could be expected to find them someday, as Tosafot explains. Either way, the contractor would be correct in our case. (The fact that the contractor was working for the homeowner at the time he found the package does not change the halacha.[7])
However, there is another factor that is likely to be overlooked in a society that does not operate according to Halacha. Even if we can assume that the owner of the money cannot be identified, does that mean that the finder can keep it? When the unknown person stashed the money away, he apparently planned to take it back at some time. We lack sufficient grounds to presume that at some later point, he decided never to retrieve the money. It is likely that he was unable to retrieve the money for some reason and became incapacitated or died without having informed someone about it. Since (virtually) everyone has some sort of inheritor, even if the owner died, there is a new owner. If, as is very possible, the new owner does not know that this money exists and is his to inherit, he could not have had yei’ush (give up hope). Since it is the presumption of yei’ush that allows a finder to take an object (including one without identifying signs), the finder ostensibly has to hold on to it and entertain the remote possibility that someone will come and prove his ownership.[8]
Why is it that in the gemara’s case, the finder could take the old lost object? One opinion suggests that it was left over from the nations that were conquered long ago, making it not applicable to a regular case. However, a more fundamental explanation is called for. In a situation in which one loses something and it is unlikely that he will ever get it back, his lack of control prevents inheritance from occurring and it becomes hefker (ownerless).[9] Therefore, if we could ascertain that the money was hidden long enough for us to presume that its owner died, the contractor could keep the money. If not, the matter would raise new, complicated questions that are beyond the scope of this theoretical discussion.