I can see both sides of the story- on the one hand, the customer is always right. On the other hand- we don't really know who the two employees are, or what was going on that they were in the parts department in the first place. The "must have been management" guy could have been called in due to a major screwup, his dog could have just died, he could just be a jerk.
We have really restricted hours- it's just me and my wife- and we live on the premises. 95% of the time if I'm out doing chores and someone comes up and honks at the gate I will open up and get whatever they need. Sometimes I say "Sorry, we're closed"