My recollection of that scenario is a bit vague, but in the 1920s Peru saw regular traffic from geologists hunting minerals, archeologists hunting ruins, and a variety of the natural sciences poking around, so you could literally run into a person with that background wandering in the wild, perhaps after a mishap that left him short of supplies and needing to join up.
There was serious political issues going on in that period, too, so a reporter, mercenary, or would-be gun runner could be encountered wandering around the backcountry, on the hunt for news.
That's all I've got.