Facilities and Alzheimer's

Today it seems, every time I go to the Internet to read news on Alzheimer’s, hoping for a cure, instead I read about Alzheimer’s patients walking out of facilities. They are found dead, hit by a car, lost in the woods, wandering down a highway, or sometimes good news, the police have found them.

My question: How does this happen when the person is in a facility being looked after? How and why does it happen? Are Health Care workers not doing their job?
My friend Carol was a wanderer, an escape artist. She tried to wander all the time. She’d be gone in a flash, when I went to the bathroom, or was on the phone. I hung a small alarm on the doorknob, so if the door moved it rang. My ears were tuned to the sound of the alarm, which went off at all times. For night the alarm was set, plus a latched lock high near the top door molding.

When she did get out, and I didn’t hear, whether taking a shower or out back cleaning porch, the neighbors called me on the phone. ‘She’s out again,’ they’d say, and I’d run after her. Neighbors were a great help, telling her to go back home, or at times led her home. We lived in a condominium complex so people looked after people. Only once I lost her, and that was in the grocery store. She had left my side when I turned around to talk to someone. In an instant she was gone, and I panicked. I knew she wouldn’t come back on her own. She wouldn’t know how too. I had to find her. I ran down the aisles looking for her, frantic, hoping she hadn’t made it to the outside door, because then I wouldn’t know what to do. She couldn’t talk, to tell someone what she wanted, and she had broken 5 ID bracelets I’d put on her wrist. She was a person lost, yet looking for something. That day I found her four aisles over from where she’d left me. Stupidly I reprimanded her for leaving my side, "Don’t go away from me," I said. Little did I know then, she wasn’t listening, or didn’t understand.

I wonder if I kept an eye on her all the time, how is it patient’s are able to walk out of facilities unnoticed? How does this happen, when there are more workers watching residents? I just don’t understand.
It seems we can track satellites, but we can not track Alzheimer’s victims.