Nobody can answer about the rules at YOUR parking lot. I'd just bring a socket & breaker bar. Use 5th gear, set the breaker bar so it lays back towards the driver. When you push the car forward it will turn and wedge the breaker bar against the lower control arm or something like that. You may have to try it a couple times so it doesn't just fall off.

I'd put it on as tight as I could get it like the others have said. That'll be ok to drive home. It probably took a while to work loose in the first place. Then torque it properly.

How did you notice it? I really hope the pulley didn't actually come off, or you may have more damage than you're telling us about.