Before they were empowered from the inside out?
What if the Holy Spirit had showed up on the Day of Pentecost and the upper room was empty, the disciples too eager to get busy building the Kingdom of God to wait for Him?
Would there be church today? Would there be the New Testament? Would you and I, as the 21st century believers even exist, lacking the supernatural continuity - day by day, year by year, century after century - with those early followers of Christ?
This, of course, is blissfully useless musing, since they did none of that. There is no record that they even entertained that option - on the contrary! They did exactly what Jesus had told them to do, went back to their home turf, armed with hope and confident expectation that what He had promised He would certainly fulfill.
Prepared to wait, for as long as it takes.
They didn't think there was something more important they could do than being together and praying.
They didn't find Jerusalem or the upper room too confining and claustrophobic to start right there. They didn't get so carried away by the global mission that they skipped important, even crucial steps in fulfilling it.
They felt a biding connection to the living Word of God and did what they had to do in order to fully align their reality with the revelation of the Scriptures. No matter too small, no word too insignificant to ignore.