We know that Abraham's encounter with the High Priest inaugurated the Lord's Supper, pre-figuring Christ's Last Supper.

Genesis 14:18 And Melchizedek king of Salem brought forth bread and wine: and he was the priest of the most high God.

But Joseph's instructions have us seeing the empty cup being placed in the sack with the corn, or grain - not yet bread.

Oh, the pictures of better things to come that we are given in the Book of Genesis!

Genesis 44:1 And he commanded the steward of his house, saying, Fill the men's sacks with food, as much as they can carry, and put every man's money in his sack's mouth. Genesis 44:2 And put my cup, the silver cup, in the sack's mouth of the youngest, and his corn money. And he did according to the word that Joseph had spoken.