the order of energy in the system can be destoryed, becoming disorder, or random entropic noise at approximately background radiation levels, as noise (quantum foam). any change from this state will require energy to create order and structure above background vacuum levels, and if the entire universe is uniformly distributed with maximum entropy at 0.1k or whatever, the odds of spontaneous ordering sufficient to provide enough mass-energy structure to create something like a proton or even a photon out of nothing is extremely small. and what even would matter a single photon?  it isnt so much that energy is gained or destroyed, but it is much more like relativity, each ordered system gains or loses energy and exchanges order/entropy in spacetime relative to each-other. one day the the universe will be so cold, all light will stop, but whatever is left will be enough for something to exist on long enough timelines im sure.
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