What the hell?!?! Missing lug nut

[SuperStretch18]

OK, so I took my son to the park this afternoon to get out of the house. Did our thing and started packing up to leave. As I'm putting my son in the car, I notice that one of the lugs on my right rear tire is missing! My car has about 5000 miles on it, and the only people that adjusted the lugs to date were when it was manufactured and the dealer that rotated the tires at 3700 miles. I guess one of two things happened:

1) Some bonehead REALLY needed a single lug nut (unlikely)
2) The dealer did not properly torque down the lugs when they were rotated

I'm not so worried about the single missing lug, as I am about others popping off as well. Any thoughts on whether this is worth addressing with them?

 

[Sveivo]

Did you check to see if the rest of the lugs were loose with a wrench? I bet they just forgot to tighten a nut.

 

[SuperStretch18]

Yeah all of the rest seemed tight. I'm still nervous though. Anyone ever bring this type of thing up with the dealer?