I think the method you described is the only sure fire way to confirm that the trailer ball is properly captured by the truck mounted hitch. While is has been a few years since I had a "pull behind" or "bumper pull" trailer, what you described is how I always confirmed that the trailer was properly hitched. I you want to get down and possibly dirty, you can look under the hitch to see if the ball has been completely captured by the movable part of the hitch.
That is one reason to have an electric trailer jack, makes the hitching process much easier.