S.C. Code § 30-7-30
A release or satisfaction of the lien of any mortgage or other written instrument affecting title to real property as security for the payment of money, made or entered into by the original mortgagee, trustee or his legal representative, or any assignee under an assignment recorded as provided in Section 30-7-40 shall be good and effectual, both in law and in equity, for the protection of any subsequent purchaser for a valuable consideration of the property affected by such mortgage or other written instrument, or subsequent creditor obtaining a lien upon such property, notwithstanding any assignment or transfer of such mortgage or other written instrument or of the obligation secured thereby, unless such assignment or transfer shall have been recorded as provided in Section 30-7-40 or such purchaser or creditor shall have had actual notice thereof before such purchaser or lien creditor acquired any interest in or claim upon the real estate so encumbered.
S.C. Code § 30-7-30