That would appear demonstrably untrue because if it were so, people would be mining this man-made litter rather than mining kilometers underground. What motivation would mining have to carry on doing so whilst it is easier to extract these materials from old products?
Well, well, well, so you are mixing multiple assumptions into a nice cocktail here.
Let me get this straght. You say:
1. Some catastrophy will somehow magically destroy the entire industrial base of the world so that modern mining methods become unavailable and we will have to dig resources out of garbage dumps.
2. The same catastrophy will leave all of human population alive, so that the resources that are currently used/bound by the human population still wont be available. Because see, we currently have to look for more resources because the resources that we have used up are IN USE by people. You take the people away, the resources that they were binding instantly become available to the remaining population. No need to dig those out of garbage dumps
So lets say that your meteorite strikes and destroys everything. As we could see in japan recently, such destruction does not come without casualties. In fact I think that their current problem is "to much stuff" rather than to little...
So I think that your perspective for the future is silly.