My local news station had an interesting story about trying to find individuals with dementia when they are lost. It gives some interesting insight into why dementia cases are different than other lost person cases. They tend to move in a direct line, downhill along the path of least resistance, stopping when they reach an obstacle. They also tend to not answer when someone calls their name.
Take a look at the video in the link above. I've tried to use the embed video script but it doesn't appear to be working. While you're there, you can check out their seven tips for helping authorities when you are faced with a lost dementia patient.