They are all gone, aren't they?
I remember I wasted hours and hours by sitting on my bed and thinking how miserable I was. I could make use of this time (these hours) in a more efficient and beneficial way. But they are all spent, aren't they? These hours are never going to come back, are they not?
Not necessarily if unbeknownst to you those endeavors that normally take up a certain amount of time come to fruition sooner, so you in effect, get the time back by not having to deal with things that ordinarily do not go smoothly in the first attempt.
Whether the cause of the "smooth sailing" is karma, or a guardian angel, or dumb luck, it might not matter; what matters is that one never can be sure that one has truly wasted time, in my opinion.
Also, many people do not even question if they have wasted time, so asking the question itself, is not a waste of time.