SANTA ROSA, Calif. — When a firestorm swept down the hillsides of Sonoma County, bringing terror to this tight grid of thousands of homes, dogs tended to rush to their masters.

But cats went in the opposite direction, ignoring the pleas of panicked owners and disappearing amid the chaotic evacuation.

Finding the missing cats that fled the October wildfires has been an impassioned quest for Jennifer Petruska, an animal lover whose home, pets included, was one of the few in her neighborhood to be spared.

Ms. Petruska has spent nearly every night since the fires tracking and trapping fire cats, as she calls them, the felines that for weeks have remained missing because of stubbornness, trauma, instinct, or a mix of all three.