。
Did anyone come while I was out?
Literal
Absence-during anyone [subject-が] was-visible [question-か]?
どなたか見えましたか uses the keigo verb 見える (to come/to be visible, honorific for いらっしゃる/来る) and the honorific どなた (who, polite). This is the kind of question you ask when returning home, checking if anyone visited.