An agent for an unidentified principal is liable on the contract to the third party no matter whether the particular transaction is authorized or not.

Unidentified Principal

A party in a transaction whose identity is not disclosed or known to the other parties involved.

Liable

Being legally responsible for something, especially in the context of debts or wrongful acts.

Transaction

A business deal or exchange between two or more parties, involving the transfer of goods, services, or funds.