Upon the inoperative date of this chapter, any remaining funds received pursuant to this chapter shall be refunded on a pro rata basis to all persons from whom assessments were collected during the 12-month period before the inoperative date, unless the secretary finds the amounts returnable are minimal and therefore impractical to refund, or the person who paid the assessment cannot be located, in which case the funds may be used for broomrape control or related research activities.