Well since not every single convention delegate is chosen through the primaries there would just be really small conventions that chooses the candidates.
But I am wondering if the parties have some requirement that the candidate is chosen predominantly through the primary process, in order to have as much public participation as possible. If that is the case, they would not have met the requirements in choosing a legitimate candidate.
That is really my point in presenting this impossible scenario.
Yeah, you're "just curious" about what would happen in this fantastical scenario, where all the ballots go missing, and mysteriously "no one voted". I'm sure it's not because you're planning something nefarious.