In the very first episode, the news reporter says Job when she reveals how the Aztec Tomb works.
Also, when Gob is Buster's assistance for the Sword of Destiny illusion, I "think" somebody calls him Job. OR it might've been during the Saw-the-woman-in-half illusion.
Over the summer I watched all the seasons a few times, and I am 92% sure Gob never mispronounced his own name.