Is any signal ever one way
no signal(control or power) is ever one way, and MUST find a way back to its origin to complete its journey.

Your understanding is correct.  While omitted for simpler diagrams, a closed return path is required for current flow (not considering charge migration in electrostatics when 2 bodies come in contact).
For example, when you use a regular voltmeter you connect it between 2 points, and a current (albeit very small) must flow through the meter for it to measure voltage.