Not entirely sure I understand what you mean.
If you are put on a radar heading by an ATC unit, and then subsequently told "resume own navigation", that would mean you resume the flightplan portion of the sector you would otherwise be on if the radar vector had not taken place. In reality this means either resume the airway and fly to the next obvious waypoint, or if cleared fly direct to the next waypoint.
A surveillance radar approach (SRA) is an entirely different thing. If an SRA were terminated without a visual approach and landing being possible, I would have thought it was compulsory to fly a missed approach and utilise a different type of approach. It would be most unusual ( except in the case of equipment or human failure) to be told to "resume own navigation" on an SRA ?
The term certainly means radar vectoring has been terminated, but it really doesn't make a lot of sense in the second example.