You just need to understand that a "path" in Gimp (ie, the thing listed in the "Paths" tab, that you can make appear and disappear using the eye icon) is just a set of instructions to draw a line, but not a drawn line (ie, there are no pixels associated to it). Of course, if you click on the eye icon in the Paths lists, something is displayed, but it's only an indication of where the line would be drawn, and it won't show in the final image any more than the marching ants that indicate selection or the dotted lines that indicate layer boundaries.

Making a lines of pixels from a path (on the current layer) is called "stroking" the path, and this can be called from two places:
- the Paths list/tab, in the right click menu of any path, to stroke that specific path
- In the image window menu: "Edit/Stroke path", strokes the "active" path.

When you stroke the path, you have the choice between stroking a plain line of a given width (it uses the foreground color) or emulating one of the paint tools (brush, pencil, airbrush, eraser...)

Paths have other uses that stroking lines, they can also be used to create selections.

AnMal
Two things I want to confirm.
1. I know nothing (virtually)
2. I have no idea what trolling is either.

As far as I know I have done all you tell me to do re:
1. working with a new (transparent) layer and placing it on top
2. Using a foreground colour other than white (in my examples I tried a very dark blue)
3. Stroking it as described.

Ofnuts.
I do understand that now but still cannot grasp that a path once stroked in a distinctive/outstanding/visible colour cannot be saved in an image!

I think we should just close this now as I appreciate the help but I think, and don't blame, everyone will be getting bored/frustrated/annoyed with my questions.

well, if you want to close this that's fine, but i think very few people here are easily annoyed by questions, whatever level they're on, so you shouldn't worry about that at least.
it's of course possible that there really is some sort of problem with your particular version of gimp on your particular os, and that's why your problem still hasn't been solved, but i think it's more likely some silly little detail we've all missed. if you want to give it a new try, just say so and i'm sure there are plenty of people here who could go through it with you step by step.

Well, it should be saved. Do this:

- create an image
- create some path in it
- stroke the path
- save as XCF
- export as PNG

If the PNG doesn't display the path, attach the XCF here.