Yeah, but neither +Paul not +Luke were there...and the Gospels weren't written when they wrote the Epistles and the Acts...
Once again I will try to explain it to you. It doesn’t matter when something is written, it matters when something is said. Jesus, when he appeared to the disciples, told them to make disciples of all nations. He also, at that time, told them to go to Jerusalem and wait for the Holy Spirit. The Holy Spirit came to them AFTER jesus talked to them.