Except for his time in Indonesia, it was his first trip out of the country.
Do you really think he just forgot to mention it???
No, I think he didn't think it was any more important to the story he was telling than the fact that my first trip out of the country was a weekend in Ensenada 20 years ago would be to any account of my life. On the other hand, the Kenya trip was important to the narrative, and he did talk about that. Do you want to know what he did every spring break during his college years? Maybe you could make up a story that he traveled to Yemen or something and demand he prove he didn't.