This whole scenario is really bizarre. Why level off at 3,000 to diagnose an autothrottle INOP? Maybe there's some legitimate reason for that in the 757. However, it is also strange how when contacting ATL Radio he does not ask for maintenance or dispatch. Meanwhile, as the issue has been handled, you're burning thousands of pounds of fuel in vectored holds at low altitude, waiting for a duty pilot to give you permission to call in fatigued. Yikes.