When you logically think through it all, it makes me wonder what Luther would have said about the matter: that is in terms of the doctrine of predestination, and faith alone (sola fede) being the exclusive requirement for salvation (for those predestined, mind you). Thus would a child who is not predestined, but cut short in life, go to heaven because without sin? Or rather, if not predestined, would the child be damned to hell a priori for ineluctable sins thereby not committed? Or, if predestined, valued by god for what would in any case have been and thus saved? Or is (or was) predestination simply the result of a de facto state of innocence: quem di diligunt, adolescens moritur (“he whom the gods favor dies young”)? And how do we assess the role of faith in salvation in such cases. Is faith only a requirement of the righteous who live long enough to be held accountable for it? Conversely if someone wasn't predestined, but has faith, is that a useless masochism?
In light tof these considerations, would the person who saved the dog be considered a hero or a knave?