where the hell do you guys shoot that you have to worry about this shit?
maybe I'm just an 'off-hours' kinda guy, but almost every time i've ever gone to any private range, I've been alone or very close to it. my old club had almost 900 members and my new club has almost 500 members. both clubs out in the burbs and no one would ever even have an opportunity to follow me out of there or wait for me outside without being noticed.
out here in Indiana, we have DNR public ranges and I do keep my head on a swivel whenever the rare occasion that I'm at one of those. there's a lot of potential for something to go wrong at any one of these places, but I only go to these when I have a very short range trip planned (need to break in a barrel with a round or two or get on paper with a new optic...maybe test out a new gun for function). but any time i'm out of the truck, so are my guns/ammo. straight to the range, straight to the firing line, straight back to the truck, and straight home. once everyone on the range knows what I have (since i've been actively shooting them), I do my best to gtfo of there before anyone can even think about trying to roll me. all that being said, I haven't even run into a single situation where I felt I was in danger of this...just staying vigilant.
leaving your truck to run into a corner store seems like it should be ok...maybe pick a better parking spot and keep an eye on the truck when you're in the store (pretty easy to do at most convenience stores i've been in with large glass windows across the whole front). if you're hungry, get drive through or take out or find a restaurant with outdoor dining area or seating that faces your vehicle with full view through a window. I've been on many a road trip and asked for certain seating from waitstaff and most are accommodating.
basically, if you don't let the situation 'make you', any jack wagon can dodge this type of behavior by just paying attention.