upon this place, and upon the inhabitants thereof, even all the words of the book which the king of Judah hath read:
upon this place.  And they brought the king word again.

They didn't want to hear anyone else, He wanted to hear someone with power.  He sent to a woman of all the prophets in the land.  Huldah began to prophecy when the men arrived, and the King received the Word of the Lord that he was after.
It was not enough to talk to a priest when the king needed to hear from God, He had to have a God called prophet, and she proved that she was called of God himself when she began to prophesy a true prophecy.  They did not have to stone Huldah, for her word was proven true.

2Kings 22:18: But to the king of Judah which sent you to enquire of the LORD, thus shall ye say to him, Thus saith the LORD God of Israel, As touching the words which thou hast heard;
19: Because thine heart was tender, and thou hast humbled thyself before the LORD, when thou heardest what I spake against this place, and against the inhabitants thereof, that they should become a desolation and a curse, and hast rent thy clothes, and wept before me; I also have heard thee, saith the LORD.
20: Behold therefore, I will gather thee unto thy fathers, and thou shalt be gathered into thy grave in peace;

Josiah received and answer of peace from a God-called ministry. . .  the ministry of a woman.