Muggles' Guide to Harry Potter/Characters/Caradoc Dearborn

Overview
Caradoc Dearborn was a member of the original Order of the Phoenix. According to Mad-Eye Moody, his body was never found.

Order of the Phoenix
At the celebratory party at Grimmauld Place for Ron and Hermione's appointment as Prefects, Alastor Moody shows Harry a photograph of the original Order of the Phoenix. Caradoc Dearborn is in that photo, and Moody comments that his body was never found.

Analysis
Given the context – Moody talking about the original Order of the Phoenix and how many of the members in the Order met their deaths – it is a reasonable assumption that Caradoc had been in some sort of battle with Death Eaters at the time of his disappearance.