Theft by finding in the United States

Theft by finding occurs when someone chances upon an object which seems abandoned and takes possession of the object but fails to take steps to establish whether the object is genuinely abandoned and not merely lost or unattended. In some jurisdictions the crime is called "larceny by finding" or "stealing by finding".
If the owner has renounced all property rights in the object, then the property is abandoned. Since theft is the unlawful taking of another person's property, an essential element of the "actus reus" of theft is absent.
The finder of lost property acquires a possessory right by taking physical control of the property, but does not necessarily have ownership of the property. The finder must take reasonable steps to locate the owner. If the finder shows that reasonable steps to find the owner have been taken then the finder may establish that the required "mens rea" for theft, the intention to deprive the owner permanently, is absent. 
In discussing the history of finding, Alice Tay collected some cases (at footnote 36) where a finder raised an unsuccessful defence to larceny on the grounds that the circumstances of finding were such that no inquiry as to the true owner was required: 
and cases where the circumstances were held to show no larceny:
An issue may arise when a person takes possession of lost property with the intention of returning it to the owner after inquiry but later converts the property to the finder's use. This is illustrated by "Thompson v. Nixon" [1965] 3 W.L.R. 501: an off duty police constable found a bag of rabbit food lying by the roadside, took it home intending to hand it in as lost property but some time after decided to keep it for his own use. He was found guilty at first instance but his ultimate appeal to the Divisional Court was upheld. The appellate court held that, at the time of finding, there was no mens rea to support a conviction of larceny. In some jurisdictions this has been addressed by statute; see, for example, s. 124, "Crimes Act" 1900 (NSW) allowing a jury to reach an alternative verdict of "fraudulent appropriation".
Some have argued that finding should not be a province for the criminal law system but that any dispute as to ownership be left to resolution via a civil suit. Others have argued that the jurisprudence gives rise to legal fictions and strained reasoning which has attracted divergent statutory law reform in different jurisdictions.