When a testator destroys their will with the intention of revoking it, that person does not have a will. The destruction does not mean an earlier will becomes the valid will of that person.
An earlier will can become the valid will if the testator re-executes it, following the formal requirements of making a valid will [Succession Act 2023 (SA) s 21]. This is known as republishing or reviving a will. A will that is revoked and later revived is taken to have been executed on the day it is revived [s 21(4)].