Paul writes to the church in Corinth,
There are two interpretations to this. Paul is looking for any prophet to endorse what he is saying, or Paul is saying that in order for a man to be a prophet, he must endorse Paul's words. The distinction is minor, but important.
If Paul is looking for a prophet to endorse his words, why? Does Paul not claim that Jesus speaks to him in visions? That would make him a prophet. If so, why does a second prophet matter? Is Paul lying about what he is writing about? Alternatively, if Jesus does not speak to Paul in visions, why listen to Paul at all?
However, if Paul is saying that any prophet would recognize his commands as from the Lord, who gave Paul that authority? It is not recorded that a group of already established messengers from the Lord gave Paul authority over establishing who is and is not a prophet.
Value of this Evidence
This is decent evidence for Paul being a false apostle. Both interpretations of this writing result negatively against Paul, because they place Paul's divine ordinance in doubt, or because Paul is attempting to assert leadership over a group of people that only God assigns.