I could only ever imagine taking a flyer down due to a corporate policy or local law I had no control over. I don't otherwise understand pulling them down unless its nefarious. I do remember an article discussing them being pulled down but I haven't heard anything about it locally. I haven't really heard any local theories though; I only see people sharing and offering prayers etc. on facebook and the occasional local news story recapping everything we already know.
Personally IMO I do not think she disappeared willingly, I think she was either a victim of someone in her life that data will point out as a potential suspect or a victim of a stranger/crime of opportunity.
Murders of strangers or innocent victims in Louisville is quite rare, but you can google "louisville woman kidnapped" and see that kidnapping and sexual assaults by strangers in crimes of opportunity happen several times a year.
I also think an accident is possible but it would be hard to get away with a hit and run and cover up in that area and there are no large bodies of water within miles of the area, so I lean more towards foul play. JMO.