And given the proximity of time and location of Paul and Jesus' lives, as well as considering Paul's prominence in the Pharisaic sect (he studied under Gamaliel), it is unlikely that he knew nothing of Jesus. On the contrary, he disagreed violently with Jesus until the time of his conversion by Jesus.
I have in various places (both Catholic and Protestant sources) seen Luke, Barnabas and Apollos referred to as Apostles. And many times, the word Disciples is used to differentiate these from the original twelve called by the Lord.
In any event, the point I was trying to make is that neither Paul nor Luke ever "knew" Jesus during His lifetime.