It's not possible that people would forget how to make and maintain all modern tech. There are just too many technical books out there; nothing that leaves a billion humans alive could destroy them all.
But it IS possible that, although they would remember how to make modern technology, they would be unable to do so. Consider the fact that we have used up all the easiest-to-access resources, particularly fossil fuels. If these calamities cause society to collapse, once it reforms it will have great difficulty re-industrializing. This is because energy will now be hundreds or thousands of times more expensive. Some places might be able to rebuild hydro-electric plants, but that's just not an option for most of the world.
It wouldn't be exactly pre-industrial; some modern tech would survive. Medicine, for instance, would still be far-superior than pre-industrial medicine. Just the knowledge of germ theory would make an incredible difference, let alone knowledge about nutrition, surgery.
So basically, the world would know how to make modern tech, but it would be logistically impossible.