Seems to me that there are two ways it could go, depending on how you take the question. If when all the tech disappears the resources reappear, I'd say it doe

Seems to me that there are two ways it could go, depending on how you take the question. If when all the tech disappears the resources reappear, I'd say it doesn't take too long at all. Maybe ten years, maybe a hundred, maybe a thousand, but nothing more than that. This is a sort of "If people with modern knowledge fall back in time" scenario. On the other hand, if the resources aren't available, ie all the iron that's been mined over the last hundred years is simply gone then we'd be pretty boned, and would probably go extinct. This is more of a post-apocalyptic scenario, except you can't even mine the I-beams out of old skyscrapers, but all the cheaply accessible metal's been mined anyways so your civilization simply can't advance past the bronze age (or wherever you manage to scrape it up to). We'd be like the australian aborigines, who lived for (if wikipedia is to be believed) an astronomical 40000 years on the continent without developing anything more sophisticated than the boomerang.