After trying to watch the press conference and filling in the gaps with what I've read here, I am 100% convinced that it was a crime of opportunity. Truck pulls up behind Mickey, taps her (damaging the bike) and with no ride home now, he convinces her to let him give her a ride home. She may or may not have been injured, and maybe is a bit disoriented if she fell and hit her head without a helmet on. He says "It'll be quicker to go down to Congress from University"...by the time she realizes he's not turning on Congress it's too late. He subdues her somehow and hops on I-10, ditches the bike, and continues on his way to go God knows what to her. That explains why she's not on the camera, why the truck turns around, why there's no evidence at the scene, etc. They want the white truck because they think he did it, they want the other truck and Olds because they think they may have seen something. MOO, of course, but with what we've been told, this is the most likely scenario.