I wouldn't expect a deity to answer that sort of prayer. You're not being sincere, just trying to test them, which many canonically find annoying because it shows mistrust; you don't need that die to land on a four; it suggests you'd use prayer to lowly ends (e.g. "Let me score a touchdown" rather than "Please solve world hunger"); it gives an easily publishable result, which no deity would characteristically accept - if they didn't want to be discreet they'd still be doing showy miracles. Studies where you pray to cure cancer or something are much stronger evidence.