Originally Posted by robertv

I think he's saying they popped off, not snapped.
And while you should be able to trust an LBS to do things like this I gotta say pretty much every bike I've ever had needed the chainring bolts tightened. In fact anytime I'm riding a new bike for the first time I check the bolts every 5 or so minutes. I have never had a new bike come from the shop without having problems with the chainring bolts. Often the crank arms aren't tightened enough either. And I try to only go to LBSs that don't suck completely.

Since your bike is fixed unless you installed the cog, I'd double check that too.