Here is my theory on Sierra's abduction:
Map
6:29 Sierra posts her snapshot to Twitter (Sierra's location is point B on the map)
6:32 Sierra posts to tumblr (Sierra's location is point B on the map)
7:11 Sierra sends text message from her phone (Sierra's location is point B on the map on her way to point C the bus stop)
7:15 Sierra arrives at bus stop (Point C)
7:15 Perp sitting in his vehicle as point D can see Sierra arrive at the bus stop using binoculars.
7:16 Perp abducts Sierra at gun point from the bus stop (point C)
7:17 Perp throws or has SL throw her cellphone from the vehicle at point E while en-route to point A.
7:18 Perp pulls up behind the building where SL's purse was found to handcuff / secure her. This might involve a trunk.
7:20 Perp discards her remaining things and evidence at the location.
7:21 Perp then leaves the area with SL, location now unknown.
The condoms and the handcuff box were a dead give away to me. This perp might have watched her on more then one occasion. He might have fantasized about the abduction thus the condoms (I'll leave the nasty stuff out).
Really the only thing missing is the box labeled binoculars. However Im sure thats something the perp already had if he was a sexual offender. IMO this is a sex offender.