Checking in, Missie, I don't know about your questions. Give them a call.
It surely won't hurt anything. All they can do is tell you no, maybe re-direct you, etc... We do need her poster up at these sites. Ask them what will it take to get a poster up. She is a missing person with her whereabouts un-determined and un-explained. She also was a minor with suspicious circumstances surrounding the last several years of her life leading up to her mysterious end of contact with any known persons. Also suspicious events concerning (authority: principal, teachers, doctors, pastor, etc... and care takers) of Deanna the few years leading up to her disappearance.
Have you talked with your grandmother again lately to check in with her? I think by doing so, you can help her remain passionate about her own personal search too for Deanna. Which could in turn trigger maybe the most smallest of detail that could help. Including your sister too that lives in another state that was closest to Deanna.
Call the sgt. you've been waiting on. Did you get the records or copies from social services surrounding your families case? There even could be an unknown case file concerning your family you may not have ever been aware of. Normally, if there's been one filing, there's normally more. I would also try to personally contact the principal of her school at the time, and the school secretary who would be responsible for filing the paperwork either way concerning Deanna, no matter what circumstances of her leaving or moving that particular school. She may have information or rumor of Deanna's next destination concerning her schooling or yours, the other sister.
I would also continue to periodically call the step father. Time is your friend, and age mellows out people, and when their time gets nearer to pass from this world to another, they begin to re-think decisions they've made in their life, and want to right the wrongs. I just really feel he knows something that could be helpful he hasn't shared. If not the bomb.
I pray some mysteries are revealed concerning Deanna. Amen!