What proof of non-existence before? In places where reincarnation is accepted and children not shushed when talking about "When i was____" and the rest of it relates to a different life such memories are often verified by their familes.
As for references to physical nature:
1) Nature recycles everything.
2) One of the laws of thermodynamics holds that neither matter or energy can be utterly destroyed but rather they convert back and forth from one to the other. Experiments with colliding atoms have left more debris than the volume of the two original atoms.
And
3) how limiting and Rather arrogant, IMO,to think this is the only reality.
Read more neuroscience, folks who only believe you physical senses, you'll learn that only a fraction of what those senses perceive makes it into your waking conscious mind. True, in varying degrees, for all of us.