Why not just ask the 8:30-12:30 girls if I could take a peek into the car really quickly, once they got back? That's what I'd have done, had I seen them before they left at 8:30pm.
But I felt like approaching girls at 12:30am in a deserted parking lot wouldn't be particularly considerate. Especially not when you're dressed all in black and leather and some really epic boots (see above), the fact that you are in actuality a really unmenacing figure obscured by your hood and the scarf covering your entire face--because you did just run there, and it's snowing, and 10 degrees out.
Of course, in an effort to not be creepy, what I did instead was walk up and down the street like a complete creeper--which would have been fine if I hadn't had to do it multiple times because these girls failed so entirely at swiping into the parking lot and getting out of the car in a timely manner! So then I ducked into an alley and observed their sluggish-ass departure undetected, LIKE AN EVEN BIGGER CREEPER.
Plus side, for the low price of $7.50 of Zipcar "driving" and skulking around in a parking lot in the dead of freezing night, I did get my phone back.
...I'm not sure this tag I'm using has ever been more appropriate.