I would take the money to the lost property office, or in a public place, to the police.
It depends on the laws of your country but in Australia, if the lost money/property is not claimed within a certain period of time, it is given to the person who found it. If that happens, its up to you what you do with it. Giving it as dana would be the most meritorious but I don't think there is anything wrong/immoral with keeping the money or goods if all reasonable steps have been taken to re-unite it with its last owner.
“No lists of things to be done. The day providential to itself. The hour. There is no later. This is later. All things of grace and beauty such that one holds them to one's heart have a common provenance in pain. Their birth in grief and ashes.”
- Cormac McCarthy, The Road
Learn this from the waters:
in mountain clefts and chasms,
loud gush the streamlets,
but great rivers flow silently.
- Sutta Nipata 3.725
(Buddhist aid in Myanmar) • •
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