It was very simple. Yang Yi easily made contact with the person Aaron sent to pick him up. It was so simple there's nothing more to say.
"Was your journey here smooth?"
Yang Yi shook his head and said, "Not smooth. We encountered an attack, but that's quite normal, isn't it."
The person supposed to leave with Yang Yi wasn't a soldier, but an intelligence officer. In short, this person wasn't from the CIA, but he was also involved in intelligence work. As for which department he was from, Yang Yi didn't ask.
These days, the United States has many intelligence agencies. The Department of Homeland Security has "homeland" in its name, but its activities aren't limited to the US mainland.
The Pentagon also has its own intelligence sources because the Pentagon and the CIA don't get along.