I feel I need to chime in here with a personal experience. When I was a student at Temple University there was a "series of attacks/rapes" on every other week. This was not covered in the news and there was no media warning issued. However, there were alerts to all students online accounts, school newspapers and flyers around school at all campuses.
On the surface if you went back to search that time you would think LE did nothing. When in reality - the students were being warned and police presence on campus was increased but none of that was made public. For many reasons - one that was explained to me later seemed odd but apparently a significant percentage of attacks reported - after an initial attack is made public are found to be inaccurate.
IMHO - you can't blame LE for not warning the people so they would lock their doors. Seriously, my friend's 10 yr old son knows the door should always be locked. No media warning would have changed the awful events that happened to Brianna - first she didn't live there so probably would never had heard them. Secondly - every college freshman gets the "safety speech" in orientation. And my last point - this description has now been out there for weeks and no one has turned him in. If it went out weeks before Brianna's abduction would the result be any different? Not sure since my crystal ball is in the shop but odds aren't that great.