Sec. 12. (a) A person is a retail merchant making a retail transaction when he sells tangible personal property at auction.
(b) Notwithstanding subsection (a), a person is not a retail merchant making a retail transaction when:
(1) he makes isolated or occasional sales of tangible personal property at auction;
(2) the sales occur on the premises of the owner of the tangible personal property; and
(3) the owner of the tangible personal property did not originally acquire that property for resale.