He may be set to Off Line status. If that is the case, then you won't see them in your list, even if you are friends. They can Whisper you, but you can't Whisper them.
Note, I don't know what Do Not Disturb does, just in case you were going to ask. The reason I bring it up is it may allow Whispering to them when they are set to that status, or they will at least show up in the list then you know you can send them at least an email. Something for you to test.
Celtic_Wolf wrote: »Thank you!!! It was set to offline, he didn't realize he did it...kept insisting it must have defaulted to that, but the issue is resolved, I appreciate you taking the time to answer me!