What he said!
The breakin was on highland..............Park in the lot past the gate.............
The thieves are likely "locals" cruising up Eureka Canyon from somewhere down below..
The break-ins are a grab and go phenomena, so probably a couple guys in a car, one to drive, one to break and grab. I'm guessing they pull in and park, then break a window on a parked car away from the street, so someone driving by wouldn't notice. The parking lot is more of a "trap", so safer to park in.
Think of parking in remote areas like this like parking at the mall. (Weird comparison, I know) Better if you aren't driving a fancy car, and don't leave valuables in plain sight. Hide them under a seat, or better still, lock them in the trunk. And since thieves have been known to hang out and watch parking areas at remote trailheads (and beaches), its better if you've got your stuff stowed before you get to the parking lot or trailhead. Show up ready to ride, or stop in a safe place some distance away, stash your stuff in the trunk, then procede to your destination.