There has been debate over whether the purported earliest NT papyrus fragment P52 used nomina sacra or not. The scant remains don’t include any locations where it might be used, but it hasn’t stopped scholars speculating based on the length of the lines and reconstructions of the text, each quite adamant about the case for their position, but for others appearing somewhat inconclusive.
While it might sound plausible to say we don’t know for a fact that nomina sacra notation began later than the NT originals, when you actually think about it, and read Colin Roberts and David Trobisch and others on the topic, in connection with the use of the codex, letter collections, the canon, and so on, it really is apparent that the use of nomina sacra was an editorial decision made at some point subsequent to the circulation of the NT documents as individual pieces of writing. Otherwise you need to imagine, somehow, all the NT authors spontaneously deciding to use this notation without consulting one another. I don’t think there is a plausible scenario for that, which is why scholars seem to be in universal agreement that nomina sacra were introduced at some later stage. Even Tomas Bokedal (very conservative, and draws upon nomina sacra as support for Trinitarian theology) wouldn’t suggest, I don’t think, that nomina sacra were not introduced to the texts some time after they were first written and at some stage during the process of their collection.