I think nutrients are generally quite stable. It's rather the vitamins that get lost, at least some of them. For example, light (and not only bright sunlight) changes vitamin C into another substance that is ineffective.

Nutrients is a very broad range of terms. Also the question of where they go is not asked specifically. The answer that I believe I can answer is the question about the amount of nutrients in "fresh food".

If nutrients are defined as that part of food which is beneficial to humans, fresh food contains, more often than not, less nutrients than other foods. "Fresh produce" is transported to points of sale, taken home and ingested. This takes time. During that time the quality of the product usually deteriorates (less nutrients). Preserving produce straight after it is harvested (such as freezing it), slows down the rate of deterioration. This means that quite often, by the time it is consumed it contains more nutrients than the fresh stuff.

It should be noted that if produce is eaten straight after harvesting, it will probably contain more nutrients.