Just wondering if there has ever been a scene in Mad Men that did not feature any employee of SC (including former employees), Betty, or Sally.

The only one I can think of is a few seconds at the end of an S2 episode when Peggy's priest started playing his guitar.

Any others?

Dick's late brother giving the package to the hotel manager, then hanging himself.

Can't be sure, but that's all I recall.

Vegemighty:

I think that was all off-screen action that we only learned about through Don's phone call to the manager.