“miraculous sign” = the people were amazed at the miracle of Jesus, but, as Augustine points out, they were undiscerning of the miracles of God which were and are even now constantly occurring: “For certainly the government of the whole world is a greater miracle than the satisfying of five thousand men with five loaves; and yet no man wonders at the former; but the latter men wonder at, not because it is greater, but because it is rare. For who even now feeds the whole world, but He who creates the cornfield from a few grains?” (qt’d in Morris p. 339)

This miracle was a sign; it’s purpose was to show men that Jesus is the Christ and the supplier of all our needs.

“prophet” = foretold in Deut 18:15 The men had their sights set too low: they understood the sign to indicate that Jesus was just the prophet when in reality He was that and the Messiah.

Deut 18:15  The LORD your God will raise up for you a prophet like me from among your own brothers. You must listen to him.

Note that the last recorded question of John the Baptist (Matt 11:2-3) is fully and completely answered in public by the Jews.

Matt 11:2-3  When John heard in prison what Christ was doing, he sent his disciples  to ask him, “Are you the one who was to come, or should we expect someone else?”