Whenever it shall be made to appear to the satisfaction of the county treasurer, either before the execution of a deed for real property sold for taxes, or, if a deed is returned by the purchaser, that any tract or lot has been sold which was not subject to taxation, or upon which the taxes had been paid previous to the sale, he or she shall make an entry opposite such tract or lot on the record that the same was erroneously sold, and such entry shall be evidence of the fact therein stated. In such cases the purchase money shall be refunded to the purchaser.