They will tell you that matter always was....
Religionists have the same problem, they say God always was...
The two sides have that COMMON fall back point.
How matter came to be is completely irrelevant to whether evolution occured. As far as I know, God created the universe, and evolution too.
The only thing we really know is that the universe exists, and evolution occurs. Those are facts. (yes I know you'll claim now that evolution is a *theory*, and it is. Just like gravity is a theory, and also a fact).
Actually, matter can and does appear and disappear as long as it does not violate the time frame under the uncertainty principle. Or conservation of mass/energy holds except for very small amounts of matter over very short periods of time. Or part of you has a small probability of temporarily existing on the moon as we speak. See also electron tunnelling. See also quantum mechanics.
There are also real virtual particles. How is this ? Theorist often predict "virtual" particles" that do not exist except if you give them a little energy bump, they will materialize in the real world with more energy than you gave them and with the exact properties you would expect.
I do not have any theory.
I think you do.
Very simple request, produce a scientist that can produce matter from nothing by doing nothing.
Mr. Sartre? Is that you? I thought you were dead, whatever that means.