Stephan's visit to the police station was uneventful, really. He wasn't arrested but asked to come to make a statement and help in the police investigation. As they did not find drugs on the other guy, Stephan could not be arrested on suspicion of drug dealing.
Thus, the only thing the police could do was request for Stephan to help in the investigation.
Stephan was prepared for this, thus did not resist and cooperated fully. He politely told them he was going to call his lawyer and would meet with them at the police station.
Everything went by smoothly and the police had no choice but to let Stephan go.
The drug dealing exchange turned out to be the sale of some rare vintage books, and though the police felt something was wrong, they had no cause to hold Stephan any longer.
After four hours of the interrogation, Stephan was let go.
