A Pointless Anecdote

One of my old bosses had a particular tic: whenever someone would make an announcment that would require a follow up, he would state "oh," to show that he was paying attention.
One day, I noticed that a particular letter had dropped off the sign in front of our building.  I picked up the letter, brought it to his office and said,

"I have something to show you."

"Oh?" he replied.

"Exactly!" I responded, placing the letter o on his desk.

He never mentioned the incident, and I wonder how he felt about one of his tics being used to play a joke on him.