In all cases where any funds in the hands of any county treasurer of this state have been lost or become unavailable by reason of the insolvency of any bank in which the funds were deposited, and not through defalcation of the county treasurer, the county treasurers and their bondsmen, in cases where the bondsmen have not become sureties on account of the payment of a cash consideration, and in such cases only, are released and relieved from any and all liability for loss of the funds.