Ignoramus3242 wrote:
Suppose that you receive a parcel that you never expected. For example
a crotch rocket motorcycle engine. There is no return address. All
reasonable efforts to find the owner fail. No one contacts me in, say,
2 weeks.

snip

I'm not a lawyer, and I live in England, so this may be of limited use
to you. According to English law I believe that for cash paid or goods
supplied in error, the person who made the error has sixth months in
which to request the cash or goods be returned (at their expense). After
that they become yours. But this is just a very vague recollection I
have from when a friend of mine was supplied some computer parts in error.

Chris