Curiosity might bring more of them to the hotel, after hearing what had happened.
The manager's ingenuity easily hit on the obvious means of misleading them, in this case.

The numbers of all the rooms were enamelled in blue, on white china plates, screwed to the doors.

He ordered a new plate to be prepared, bearing the number, '13 A'; and he kept the room empty, after its tenant for the time being had gone away, until the plate was ready.

He then re-numbered the room; placing the removed Number Fourteen on the door of his own room (on the second floor), which, not being to let, had not previously been numbered at all.

By this device, Number Fourteen disappeared at once and for ever from the books of the hotel, as the number of a bedroom to let.
Having warned the servants to beware of gossiping with travellers, on the subject of the changed numbers, under penalty of being dismissed, the manager composed his mind with the reflection that he had done his duty to his employers.