How does the second person claim his right to the gift that he accepted and left with the giver, then the giver sold it without his knowledge, and what is his argument for its ownership after the offer and acceptance?

If a person bestows a gift upon another, this gift does not become binding on the giver until the recipient takes possession of it. If the recipient does not take possession of it, the giver is permitted to retract their gift, and selling it would be valid. However, if possession has occurred, then the recipient's ownership of the gifted item has been established, and the giver is not permitted to dispose of it except with the recipient's consent; otherwise, that would contradict noble character.