Tosfot, Kiddushin 59a

“If a poor person turns their cake, and another comes and takes it [the person who took it is called a wicked person]” - Rashi explains that this refers to a cake that was ownerless. However, this is problematic because we learn in Baba Metzia 10a that if one found an ownerless object and fell on it or covered the object with their garment, and another person comes and takes it, then it belongs to the one who took it. Similarly it also says there that if a poor person falls upon some gleanings from the corner of a field, or spreads their garment over it, we may remove that poor person from [the gleanings.] So therefore, why is the case with the poor person turning a cake different?? Rabbeinu Tam explains that the prohibition to take the cake from the poor person is only applicable specifically when the poor person desires to profit from the wages, or when he or she desires to purchase one item and another preempts and purchases it. [AJWS translation]