Did you read all three parts? They laid the groundwork by alerting local police and store owners about the counterfeiter probably living in that area of Manhatt

Did you read all three parts? They laid the groundwork by alerting local police and store owners about the counterfeiter probably living in that area of Manhattan and got lucky because the neighbor's apartment caught fire and the building owner threw out some of his burned possessions, including the plates and some counterfeit bills.