I am such a mollusk

I just called my brother at work to let him know that his phone doesn't seem to be working for incoming calls at the moment. I got some guy who said my bro was with a customer and couldn't talk to me right then.

"Okay," I replied. "Please tell him his sister called, and to phone me back on [his home number]."

It was only after I hung up that I realised the flaw in my cunning plan.