I would have proceeded a little differently, I suppose. In Oregon we have a history of cases of found money not being returned to the finders.
If turning the money in, in a state which has treasure trove laws (such as Oregon), DEMAND a receipt that is dated and signed by someone in authority. In Oregon, if the money is not claimed within 6 months after notice being published, it becomes the sole property of the finder.
But the finder must also be able to state conclusively what the money was composed of, where it was found, and give details of why it was "abandoned." Thus, someone dropping off drug money to escape prosecution would still have to pay taxes on any money they "recovered" from the police. That's one reason why so few people claim "found money" here in Oregon.
In several other states, however, the concept of treasure trove does not exist legally. In a few states, if you find something, like $150,000 say, the state legally gets to KEEP it, and the finder gets nothing. A smart TH'er in that state will demand a 20-30% finder's fee AT MINIMUM before turning over any portion of the money. Until such a fee is forthcoming, the state is entitled to ZIP, and the burden of proof remains with the state to prove the funds even exist.
If there is no finder's fee, the money should be preserved/protected in a locked safety deposit box until a disposition can be made, and proof of ownership has been established.