I often speculated that this was so and indeed wondered why I’d never heard or read it. But alas, it is a hypothesis that has popped up in various places. Stanley Porter, in a lecture attempting to answer this question, referred to this passage in Weiss and so I began to read (I had not read it, to my shame) and I found this:
For myself I feel bound to say, whether others support my views or not, that this mode of treating the problem seems entirely unsatisfactory and unconvincing. I lay no stress upon the historical difficulty, that the struggle with the Nazarene churches can hardly have left Paul with time or inclination to gather detailed knowledge of Jesus’ life or with leisure to assimilate it (Gal. 1:22). There is a more important point to consider. I must adhere to the statement that the vision on the road to Damascus is only intelligible on the supposition that Paul recognised Jesus in the heavenly vision. He may have heard a personal description of Jesus from the first disciples or from casual observers; but could such a description have enabled him to recognise Jesus? If we seriously consider the meaning of this vision, we are forced to conclude that the features of the earthly Jesus must have been known to him, seeing that the vision showed him the glorified Jesus. And I cannot but wonder how the whole school of modern theology has been able so readily to reject the best and most natural explanation of these difficulties, namely the assumption that Paul had seen Jesus personally, and that the sight had made an indelible impression upon him, perhaps unconsciously or even against his will. “We need not consider the possibility that Paul the Pharisee may have known the Galilæan prophet in person. The possibility naturally exists, but that it was ever realised there is no certain evidence in our sources of information.” Thus Kölbing (p. 109). One indication, at least, we have in the considerations above detailed, which show that a literal interpretation of the vision presupposes Paul’s personal knowledge of Jesus. But the problem may be more directly attacked by an opposite line of argument. Where is there a single syllable to show that Paul had not seen Jesus in person? The words of the exalted One, “I am Jesus, Whom thou persecutest,” given in the three accounts of the conversion to be found in the Acts (9:5; 21:7; 26:14) are no proof that Paul then saw Jesus for the first time; they were spoken because Paul saw no figure, but only heard the voice. It would have been an obvious course, both for the author of the Acts and for Paul, to declare the very surprising fact that Paul had never seen face to face the Lord, Whom he so zealously served. Yet we find no trace of any remark to this effect. -Johannes Weiss, Paul and Jesus, trans. H. J. Chaytor, Harper’s Library of Living Thought (London; New York: Harper & Brothers, 1909), 39–41.