What does the chain look like at the broken link? Plates spread apart a bit? As for the customer service part of your post, did you speak to the owner or manager? Did you suggest, calmly and quietly, that replacing a snapped, new chain--a simple job, as Ed points out--sooner than 2-3 days would be in the LBS's interest to maintain customer good will in the local cycling community...especially if there's competition nearby.