Idaho Code § 67-504

If, on the day the governor desires to return a bill without his approval and with his objections thereto to the house in which it originated, that house has adjourned for the day (but not for the session), he may deliver the bill with his message to the presiding officer, clerk, or any member of such house, and such delivery is as effectual as though returned in open session, if the governor, on the first day the house is again in session, by message notifies it of such delivery, and of the time when, and the person to whom, such delivery was made.