This brings up the question for those who are current or former SAR. I know that every missing person search is different but is there any distinctive info or stats on missing people who are developmentally challenged and their odds of survival as compared to other missing people.
The best reference I know of is Robert Koester's book "Lost Person Behavior". See
http://www.dbs-sar.com/LPB/lpb.htmKoester has analyzed a tremedous number of cases and developed statistical patterns. He has chapters on children of various age groups, and mentally challenged people. There is no way I can summerize all the information here, but he says
"Thus the behaviour patterns are a blend of Child and Dementia. Mentally retarded adults best match the equivalent child age, with the exception of having an older, stronger body. Unlike children, few of these subjects get lost taking a shortcut. Almost all are unresponsive (93%). The subject will not travel to an identifiable target. Many are found in structures (including yards and vehicles) or along a road. They will travel into brush or structures to seek shelter. They are attracted to water features. Much like children, some may be attracted to animals or other favorite objects." Note that "unresponsive" in this context means that she will not respond to searchers calling her name.
Good luck on the search. Don't give up hope for a good outcome, people often survive much longer than we think possible.