Nice map. I don't know one single thing about the area, but after having been on WebSleuths for five years, the Nature Preserve sticks out to me like a big red flag.
Subie, I feel for you and your parents, and like so many, think of you every day. Another thing I've noticed over the years is that the loved ones of someone missing just have to take the bull by the horns (as you already have!!). Unless LE forbids you not to do it, organize a search. You may be waiting forever to get "permission." Talk to the CUE Center, or less formally, get together with friends. Someone else can volunteer to keep track of areas searched. You are doing a great job.
ETA: Holy cow, I just googled the nature preserve, and there is a lot of kudzu and such to search. :cry: