What kind of fallacy is it if one attributes a cause to chance when a cause is unknown? e.g., Scientists don't know why X, therefore X must be due to chance.
Take for example the masses of leptons. There's no known law of physics that governs their masses (yes, there's the Koide formula, but that's purely empirical). Some take this as evidence that the relative masses of leptons in our universe are due to chance, and that there are other universes where the roll of the dice had a different outcome, and the masses there are different. This seems premature -- we may someday find a such a law.