It is not unusual for a spoke to break in a new wheel, particularly low end wheels like yours. This is because they are nearly all built by machines and the spoke tension varies around the wheel. A good shop will retension new wheels before they're sold which goes a long way towards preventing breakages but not all shops will do it will do it for all bikes.
Now that you've had a breakage, keep an eye on things because you may have other spokes about to go.
A properly tensioned wheel will go for a long long time without any truing or spoke breakages. Your bike shop would have checked this out in the repair so you should be right from now on. I've only had one wheel that refused to behave and that was hand built, but I've always suspected the drive side spokes were too short (sold the sod now)