。
While you were out, a Mr. Brown came by.
Literal
Absence-during [time-に] Brown [quotative-と] say person [subject-が] came [emphasis-よ].
とおっしゃる方 uses the keigo verb おっしゃる (humble form for 'be called') with 方 (かた, the polite word for 'person'), respectfully framing the visitor. 留守中 (during absence) marks the timeframe. よ delivers this as new information for the listener — a typical 'while you were out, someone came' message.