Did Siddhartha Gautama Buddha ever deny the existence of a divine being?
Actually, Yellow Rat’s answer does not imply Buddha denied the existence. In that dialog, Buddha was teaching the Noble Truth. And yes, you need not concern about this in the Noble truth. Nonetheless, in the conventional truth, one should not deny the existence of heaven as one of the six rebirth destinies. If you read the canon (including Theravada’s canon), there are various dialogs between Buddha and heavenly beings (divine beings). Thus, we should not deny their existence, we just need not be concerned about them if liberation is our goal. Note that heaven is not eternal in Buddhism (that is also why Buddha refused to answer in Yellow Rat’s quoted dialog because eternal view is a wrong view).