My workplace parking lot is adjacent to a main county road, and people occasionally pull into it after hours for various purposes. Usually, they are checking maps or GPS systems, or answering phone calls or text messages, in the decent weather, we sometimes get "visitors" who are too cheap to get a hotel room for their amatory endeavors. Once in a while, someone with car trouble will pull into the lot. In the wee hours of the morning, the local constabulary often parks in the lot, which gives them a good vantage on the main road.
Typically, I will approach a "strange" car in order to ascertain the intents and purposes of the occupants- I always preface a conversation with, "May I help you?" I like to let people know that I am not immediately hostile to their presence, but I won't brook any nonsense. Should the occupant(s) actually need assistance, directions given, help with a flat tire, I can typically get them on their way in a few minutes. If I can't be arsed approaching a car, I will bust out a two million candlepower spotlight we have on hand, and will shine it across the parking lot into the car. This technique, which one of my co-workers is inordinately fond of, invariably convinces people to leave the premises. Typically, though, I like to know who is on the premises at any given time and, more importantly, get them off the premises in timely fashion. I cut some slack during the blizzard for a local guy who parked his car in our lot overnight because the side streets were a mess, and I generally get contact information for anyone who cannot move their car due to mechanical problems.
In the past two weeks, we've had a strange trend. I haven't personally experienced it (I've been working the graveyard shift lately), but two of my co-workers related a half-dozen incidents in which people have stopped in our parking lot after hours, sometimes as late as 11PM, and have wandered around the parking lot, checking out their smartphones. All of these individuals have been similar demographically... all well-spoken males of similar age and ethnic background. As it turns out, all of these gentlemen belong to a geocaching or waymarking (I'm not sure which) club which has chosen coordinates in our parking lot for their "scavenger hunt". They're a nice bunch of harmless eccentrics, but it would have been good of them to let us know to expect a slow but steady stream of visitors at odd hours. At the very least, it would relieve them of having a gruff, no-nonsense employee growling "We're closed!" at them.
For details on geocaching, this is the go-to site, for waymarking, go here. If you get involved in the hobby, I'll probably see you within a few months, just don't take it personally if I growl at you if you arrive after dark.