Answer:
The answer is - Promissory estoppel and Fraud
Explanation:
The cause of action that might be useful in the scenario is the promissory estoppel and fraud. The Promissory Estoppel is a judicial doctrine in contract law in which the court prevents or "estop" a person from going back on their word and therefore allows the affected person recover on the promise or contract which he relied on and due to which he suffered a loss.
Fraud is an act of deceiving others by intentionally using false or misleading information for one's gain and therefore depriving the other person of money or property.
The hiree can therefore sue the firm or supervisor with the use of promissory estoppel and fraud as a cause of action.