Only an attorney can advise if the situation is discrimination. Employment lawyers will usually review the facts for free. As long as you don't state your assumptions as facts, it should be easy for an employment lawyer to apply law and make a determination.

If the other store is actually hiring, wouldn't they be advertising help wanted? Find their ad and apply. When they ask how you heard about the job, tell them you are a current employee at store blah blah blah and see what happens.