No theory is ever proven. None. Ever.
With the exception of pure mathematics (without any real physical parameters).
Thank you for the correction. I should have said "no scientific theory is ever proven." Which is, of course, the subject at hand.
"Proof" as in "Proof of Quadratic Reciprocity" is only possible in math and logic.
"Proof" as in "beyond a reasonable doubt" or "proponderance of the evidence" is the best we can hope for in the real world. Things like germ theory, atomic theory, the theory of evolution, and so forth, are "proven" in this sense of the word.