Why couldn't Paul and Titus simply send each other a message to coordinate their meeting?
In that ancient era, ordinary postal delivery, telegraph, telephone, or similar messaging did not exist. Travelers therefore could not drop a note or wire ahead. Paul and Titus had made an agreement to meet at Choas, but Paul had no way to learn why Titus had not arrived.
Les explains that in the ancient world they could not just drop a note in the mail, or send a telegraph, phone, or anything like that. He notes that how they communicated in ancient times is hard to understand, but somehow Paul and Titus had made an agreement to meet in the seaport town of Choas, which was the ancient city of Troy. When Paul came to Choas to preach Christ's gospel, a door was opened unto him of the Lord, but he had no rest in his spirit because he did not find Titus his brother. With no means of communication, Paul had no way of knowing what had happened to Titus or why he was not at Choas at the set appointed time. Les adds that while Paul was distressed about Titus, the Lord came on him with something totally different, contrary to what he had thought he was going to do, and the two were almost a clash in the man's thinking.