If we somehow destroy our current civilization, then world population will plummet from starvation, especially in the third world that isn't fertilizer-self-sufficient.
And we'll still have plenty of raw coal + recyclable metals.
We won't have any raw coal. All raw coal is hundreds of meters below ground because everything that was easily accessible was already dug.
In my country hundreds of years ago people were gathering coal lying on the ground or picking it with a shovel in small holes. When oil was first found it was basically pooling on the surface or required a very shallow hole, nothing more than a deep water well, to reach.
Not only those, but a lot of other easily available sources have already been completely used up. There might be some that are overlooked in very sparsely populated, hard to reach places like Russia, Brazil or Antarctica. But the same reason why they have not been found and exploited would be why a new attempt at civilisation will also have hard time trying to find it.
And we'll still have plenty of raw coal + recyclable metals.