Ok, so, when reconstructing natural proto-languages, those protolanguages are almost never attested. Historical Linguists are basically making educated guesses and throwing darts against a wall when making the Proto-Indo-European hypothesis, it was just that the evidence was so compelling that linguists (and, most humans) believe it. For all intents and purposes, it's a really good guess.
The issue with my conworld? Classical Zispoel and Proto-Ytosi-Itaush are still fully attested languages with exactly 2 and 1 native speakers each, all still technically living.
To make matters worse, Lozerief is kind-of a scientific genius, and Pagjom is the literal Hero of Language. Together, they could reconstruct Proto-Zispoel and see what a god-awful, horrifying shit-show it was.
The idea that my characters could derive my god-awful, good-for-nothing protolanguage is, somehow, deeply disturbing to me. I think they would realize they were in a simulation if they did that.