I am a local and to clear things up, there wasn't an alert right away (the next day a at the evening news, and even then there wasn't an abduction connection, people thought she was lost). Even when they identified the make and model of the car there were no road blocks, nothing. Just a BOLO for it. But from what I understand by the time it shortly after the release of that info, they found the car and had their investigative eyes on BC. The community was encouraged to be on the lookout but not to go actively looking.
I don't believe that BC was a repeat offender. He was sloppy and careless. First, the first girl he allegedly accosted wasn't a vulnerable exchange student. She was a girl that was able to give a description of him and his car and the ruse he used. A more experienced criminal wouldn't have let her go (think of Ted Bundy). Second, if he had committed a crime before, I don't think he would be driving something as unique as a Saturn Astra. Third, I think the window between when he abducted her and killed her was narrow, not because he was experienced but the opposite... Because he hasn't had time to master his torture techniques (in comparison to killers like Robert Ben Rhoades or David Parker Ray). Lastly, he didn't have time to rehearse a better alibi than "I was playing video games" or "I gave her a ride, she panicked when I drove a different way and I let her go" I think he is just egoistical and thought he was smart enough that he could get away with it.
That said, there was a long search of the abandoned buildings and Creek that runs near his house. Locals thought for sure they were going to find something with the amount of effort they put into searching that building. But they haven't said what they've found.