Just thinking out loud (figuratively) here. I live in a smaller community than Brooklyn, IA. But similarly rural, agricultural, etc.
I tried to envision someone approaching me, someone I don't know well but who is still familiar enough for me to feel trusting towards.
Lots of folks fit that category here. Many people I don't really know but who are familiar faces from around town.
Ok, so if MT was taken and is alive, we don't know if someone drove her out of the area, or is keeping her nearby somewhere.
The thing is, all those people have their own roles in the community. Their own family, neighbors, jobs, etc.
If someone here kidnapped someone and drove away with them, certainly those other neighbors, family, coworkers etc would notice if (the potential perp) went missing. Hopefully those folks would also notice if someone was acting odd or spending more time than usual in odd places (barn, cellar, field, "driving around" etc).
What other scenarios would work? An isolated person, maybe, retired or off work for the summer, someone without friends or family nearby to notice? Or someone who is part of why I call the 'troublemaker' community already -- the druggies etc who are frequently in trouble and known to LE.
So hard to imagine that all folks in likely categories haven't been looked at already... It does lead to the thought of someone not from the local area, who either took her away (but was also known to her? from school perhaps?) or who is in the part of town where strangers are expected -- motels? Jobs that hire seasonal workers? Maybe someone whose job just finished a month ago, so that they're not currently being noticed as absent, but whose family elsewhere doesn't expect them home or can't check up on whatever story they were told about where that person was expected next?