>I would reconsider that type of interface. I use a close button on the type of child form you are talking about instead of a save button. That way, it is clear to the user that a save has not actually taken place. Then, if a cancel is later done (as in your example) the behavior is exactly as one would expect. That is, upon a cancel, the value returns to the last saved state.

So your users click "Close" and the data is assumed saved? What if they don't want the changes they did to the child? Do they have to cancel the parent to cancel the child changes then go back and edit the child again?