פירוש על קידושין 99:12

In both sections, a husband appoints an agent to betroth his wife and gives the agent instructions as to where to betroth the woman. If the husband tells the agent to betroth the woman in a certain place, she is not betrothed if the agent betroths her in another place. In such a case we can assume that the husband wanted the betrothal to be performed in that specific place.
However, if the husband merely tells the agent where to find the woman, the husband does not necessarily care if she is really somewhere else. He was only helping the agent locate her. Therefore the betrothal is valid no matter where the agent eventually finds her.