A family came to us from the north on ever Shabbos and brought flowerws. We alter saw that there was a shekel in the flowers, we called them and they said that theyprobably dropped it and we could abviously keep it but I am concerned that maybe it was from the seller or other buyers and I’m not sure what to do with it?
You can keep the shekel. Even if it was from the seller or the other customers, you didn’t find it until a while later, and the shekel has no siman. Therefore we consider it to be after yiush, and you can keep it. As a side point, as with other found items, maser has to be taken from it.
CH:M 262-3. Even though it is a small amount of money, we still say that a person is aware of his money. See Igros Moshe Y:D 4-23, Hashovas Aveida Khalacha 5 ftnt. 8 in the name of R’ C. Kanievsky shlit”a, and ybchl”ch R’ N. Karelitz zt”l.