Richard Brown runs Proof Culture, a sneaker accessory company, out of his Ohio home. As a small importer, he's struggled to navigate toward tariff refunds. Daniel Lozada for NPR hide caption toggle caption Daniel Lozada for NPR The news on his phone left Richard Brown so stunned he stumbled past the exit of the bagel shop where he was grabbing breakfast. Then, he couldn't find his car in the parking lot. On that February day, the Supreme Court had struck down most of President Trump's tariffs, which business owners like Brown had been paying for almost a year. The thoughts came to him in a jumble: How would U.S. Customs refund the duties it had illegally collected? When might Brown get his money back? As he trudged toward the answers to those questions, Brown kept an audio diary that he shared with NPR. And his experience illustrates something that's raising alarm bells among trade experts: the prospect that thousands of U.S. businesses may never get back the billions of tariff dollars the U.S.…