Chains shouldn't just fail like that, cheapo or not. Unless they're gay, LBS should warranty it. Not that it should matter but was the chain too short or chainrings bent? There could be heaps of reasons.
How does sexual preference have anything to do with bicycle warranties?
Read the site rules more carefully if you plan on sticking around.
As mentioned, it could be any number / combination of reasons.
Low-end Shimano chains have put a lot of time and effort into earning a fairly piss-poor reputation.
Unfortunately, they're also specced on the vast majority of new bikes.
Ditch it for a SRAM / Wippermann, and that should hopefully solve most of the problem.
Learn about which gear combinations to use, and which to avoid. Your user's manual should hopefully cover it in more detail, but...
Don't EVER use the smallest ring / smallest rear cog together - will put huge sideloads into the chain, and an even bigger amount of torque through only a few links.
Almost guaranteed to blow/stretch just about any chain under full power.
Biggest ring / biggest cog - the same badly diagonal chainline, only now your derailleur is under excessive stress.
Back off the pedals when shifting.
I still have a piece of chain from a school camp K-mart special around here somewhere, twisted 45 degrees over 2 links, after it ghost-shifted on me under power.