I'll grant you that there is no Scriptural support of either having met Jesus during his pre-Resurrection life. However, we know that Paul had more than one direct encounter with the Lord, post-Resurrection.
I think the odds are pretty good that both Paul and Luke were direct witnesses to Jesus during his ministry. Both were prominent men, and lived in the area. Given the stir Jesus created, they were likely exposed to Him. Although, I AM simply speculating.
See what I just wrote in #285. Luke was, if I remember correctly, a Syrian from Antioch; however, it is not unreasonable to think that his travels would have taken him to Jerusalem. I don't think there is any need to "split hairs" over this, since there is no disputing the fact that Paul was not a follower or supporter of the Lord during His lifetime and there is no reason to believe that Luke was either (although Luke did not share Paul's hatred of Christians).