It has been since buried deep in the thread, and I cannot remember who said it, but I thought it needed to be pointed out.
Somebody said that for a prophet to merely "miss it" doesn't constitute being a false prophet. Rather, to be a false prophet, one needs to prophesy something that leads people into idolatry. And so long as nobody does that, they aren't "false." Such, which is a common teaching in the prophetic movement, is simply a naive understanding of what the prophetic person and their utterance truly is. For when we truly examine what the prophetic person and their message is, then to spot the counterfeit is easy.
First, Moses says "The Lord shall raise up for you a prophet..." I like to put emphasis on the idea here of raising up. Like Ezekiel in the valley of dry bones, the prophetic man is truly a person of the resurrection. That is, who they are and what they say issues out of being "raised up." Without this raising up, they cannot be prophetic. And without this raising up, one can never hope to speak something to a valley full of dry bones that has the ability to not only put flesh on them, but cause them to live. If this prophet has not been raised up, then what hope has he to raise a valley full of dry bones, yet alone to breathe life into them?
Secondly, one must be sent by God. "Whom shall I send? Who shall go for Us?" asked the Lord when searching for an Isaiah whom He could send. And this forever must be the basis of one's speaking- that is, one's being sent. For, as Art Katz has pointed out, there is a difference between "went" and "sent." We have a lot of people going to and fro, and doing a lot of great things in the name of God. But how many do we have that are going to and fro that have truly been sent?
And it is the issue of "sent" that distinguishes the true prophet from the false prophet. The false prophet might indeed have a prophetic calling on his life. But unless he be sent and given a message, he will be speaking out of keeping with his calling. He will be speaking "presumptuously," for the Lord did not send him.
And this was the complaint of Jeremiah against the false prophets of his day. Not all of them prophesied people so as to lead them into idolatry. Rather, they were prophetic people who had a message of peace and comfort to the nation of Judah suffering at the hands of Babylon. Yet Jeremiah says they were false because their message didn't have it's origin in God's sending. "I did not send these prophets, but they ran. I did not speak to them, but they prophesied."
There was a great hurt in Jeremiah's heart over this very thing. For the prophets claimed to have a message from God, which in time, proved to be false. These men "missed it." And it wasn't to Jeremiah the issue of growing in one's gifting. Rather, it was the issue of God's sending. For God qualifies those whom He calls, and He equips those whom He sends. As the Lord said of the prophets He would raise up, "I will put my words in their mouth and they shall speak all that I command them to speak."
If there is anything a prophet is, he is real. Being a prophetic messenger called and sent by God is ultimately the issue of reality. Has God called? Has God sent? If so, then the man called and sent will have a message burning on his lips that he shall speak at God's commanding. And if the prophet is presumptuous to speak a message in the name of God that God did not give him, then then while God might have called him, He did not send him. And if God did not send him, then the prophet is playing make-believe. Or as Jeremiah said, prophesying words out of their own imaginations. Which is to say, not of God. Which is to say, it is not real, and it is false.
For as Moses pointed out, the one whom God sends will have their message come to pass, because it was God's word, and God's word will not return to Him void. It will accomplish the thing He "sent" it out to do. But the message that does not come to pass is obviously, according to Moses, not of God. Such a person, the Scriptures teach, is not sent.
So, you see, the issue of "missing it" is much greater than silly doctrines that say, "Oh, I'm just growing in my gift." The issue of growing in one's prophetic gifting is never considered in Scripture. The only things for which the Scripture is ever concerned, has the man that is purporting to give a message in the name of God one whom God has raised up, and is that man sent? For if he is, then not one of his words will fail. For he is a real prophet. All others, simply are false. They are false not simply because they said something that ended up not being true, but because they were not true to begin with.