away from (one's) desk
Not at one's desk at a particular time. This phrase is typically said in an office environment on another person's behalf (as by a receptionist or assistant). I'm sorry, Mr. Medina is away from his desk right now. Can I take a message?
*away from one's desk
Fig. not available for a telephone conversation; not available to be seen or spoken to. (Sometimes said by the person who answers a telephone in an office. It means that the person whom the caller wants is not immediately available due to personal or business reasons. *Typically: be ~; Step ~.) I'm sorry, but Ann is away from her desk just now. Can you come back later? Tom has stepped away from his desk, but if you leave your number, he will call you right back.