LOS ANGELES — For more than two weeks last month, Josie Gower shuffled between her friends’ spare bedrooms and couches while her own home in Montecito, Calif., was under evacuation orders because of the devastating Thomas Fire. So on Monday evening, she told her adult children she was grateful to sleep safely in her own two-story home.

But just before 3 a.m., Ms. Gower, 69, and her boyfriend heard what sounded like an explosion and they rushed downstairs.

When Ms. Gower opened the back door, she was swallowed by several feet of mud that overpowered her grip on the door frame and sucked her out of the house. Her boyfriend, Norm Borgatello, was swept away and pinned by a boulder against a fence. For more than six hours, he fought to keep himself alive. “Josie! Josie!” he would shout. But he never heard from her again.

Firefighters found her body nearly a mile away Tuesday afternoon. The only way they could identify her was by her fingerprints.