All persons to whom blank license stock has been issued as herein provided, shall turn over and deliver to said director all mutilated, voided and unused license stock and unsold licenses and each of said persons authorized to handle licenses shall be held accountable for all unused license stock and all mutilated, voided or unsold licenses not so turned over and delivered to the director.
Provided, that when satisfactory proof is presented to the board of examiners, of unavoidable loss or destruction of the above the said board may relieve the person charged with accountability therefor, and order repaid to him any moneys already paid by him into the treasury on said account.