I'd give the "Glomar response." Neither confirm or deny. Even denial gives away information that is useful. Why would Trump want the world to know he was bluffing? There is a reason the last man standing doesn't have to show his cards, unless met and called.
First, he wasn't bluffing. He said he hoped that no tapes were available. He never said he had tapes or recordings.
Second, he must state that there are no tapes. Otherwise, he must deal with this: Congressional investigators demanded Friday that the president turn over within two weeks any recordings he made of his conversations with former FBI director James B. Comey, as President Trump refused to answer questions about whether such recordings exist.