Ok, here's the pre-requesite "Open carry would've prevented this."
Now that we've got that outta the way, lol...
In all seriousness, I buy and sell pretty frequently though my local gun site, and I've never had anything bad happen. But I am prepared for the worst. Every. Single. Time.
That doesn't mean a friggin ankled revolver. My G22 is immediately accessible at all times. Will this 100% prevent something bad from happening? No.
But it's the risk you take.
"I'll have a Coke..."