Almost every cichlid will display vertical barring when stressed.
Below are a couple pics of young pearsei to compare.

and below a young melanurum (AKA synspillum)

the idea that your LFS cheated you may be a bit over the top.
Unless they got the cichlids from a reputable dealer, they may also have been punked.
With all the random hybridizing these days, they may have received the fish as a trade in, and may have been told they were black belts. And most LFS employees can hardly tell an African cichlid from a Mexican cichlid, or a Tilapia from an oscar, so any purchase made unless you have done serious homework, or are an expert must be taken with a grain of salt.