Why did the Prophet (peace be upon him) not punish the merchant who cheated, and can this Hadith be considered evidence against the permissibility of punishing a cheating merchant?

Fraud in sales is a major sin, for the Prophet, peace and blessings be upon him, said: "Whoever cheats is not of me." There is no specific punishment for it; rather, it is subject to discretionary punishment (ta'zir) determined by the ruler according to what serves the public interest. The ta'zir should be what achieves this interest. The ruler may deem that ta'zir is achieved by seizing the fraudulent item and donating it as charity, or destroying it, or by physically punishing the cheater. The ruler is permitted to punish the fraudulent merchant if he sees benefit in doing so.