Honestly, Jack was not paying too much attention to what Bob was saying. Although every word he spoke was a potential disaster waiting to happen, Jack had noticed that praise did not seem to have any effect on him or the universe at large.
For example, Bob calling Jack a being of supreme power made no difference in reality. So as long as he was singing praises, the consequences of him speaking could be managed. This was a rather advanced way to control what Bob said, and could not be recommended to amateurs or those handling a Bob for the first time.
So as he used his ship like a celestial sledge hammer, smashing through ships, and his crew members ran below deck to man the cannons and test them out, the only thing he paid attention to in regards to Bob was whether or not he was paying compliments. Therefore, Jack missed when Bob was interrupted, and he missed the expression Bob made when he was interrupted.
