This happened to my mom about 7 years ago...4 days, I was out of town and when I got back couldn’t reach her by phone - dashed to her house, no answer at the door, let myself in.
Found the bathroom locked, yelled mom, mom - no answer, scared me to death. It was summertime and about 96 degrees inside her house. Picked the bathroom lock and found her. No water in tub, but dehydrated from high heat in house. Scary incident - was in hospital 2 weeks....now under full care with Alzheimers - sickening desease, she doesn’t even remember me anymore.