What happens if the preempter and the seller confess, but the buyer denies the claim of preemption?

Primary text

If the preempter and the seller confess, but the buyer denies, the seller must return the slave to its rightful owner. Preemption is not established. The seller cannot demand anything from the buyer because, outwardly, the sale is valid, and the buyer has already paid the price, which was apparently his property.