What did the Lord reveal to Paul at the same time he was distressed about Titus?

At the same time Paul was distressed over Titus not keeping his appointment at Choas, the Lord revealed by a vision that Paul was to go over into Macedonia, or Greece, and preach the Gospel there. He was to obey the Lord's call across the Aegean and begin ministry in Macedonia.

Paul had no rest in his spirit because he did not find Titus his brother, so he took his leave and went from thence into Macedonia. At that same time, the Lord revealed by a vision that Paul was to go over into Macedonia, or Greece, and preach the Gospel. Though he had lost track of Titus and did not know what had happened to him, he was obedient to the Lord's call to go across the Aegean and begin his ministry in Macedonia. The context notes that Paul was pressed down, distressed, and suffering, yet always triumphant, a lesson that he was as human as we are, with the same passions, appetites, and feelings.

Acts 16:9

And a vision appeared to Paul in the night; There stood a man of Macedonia, and prayed him, saying, Come over into Macedonia, and help us.

What did the Lord reveal to Paul by vision while he was waiting for Titus?

While waiting for Titus at Choas and distressed by his absence, the Lord revealed by vision that Paul was to cross into Macedonia, or Greece, and preach the Gospel there. This vision directed his ministry across the Aegean, and he obeyed the call despite not knowing Titus's situation.