Hello99,
I’m not sure what you mean. Do I need to cite a source that a siman only works during the baking?
Do I need to cite a source that intention isn’t sufficient?
It seems, BTW, that until you brought it to there attention, they were certifying the muffins without concern for bittul at all. While it was the only muffin with that tzurah, they were apparently relying on the tzurah despite the fact that
1) It was made for mass distribution
2) The tzurah was certainly not made as a specific dairy designation (although I think the R’ma, who is mattir fleishig Shabbos bread based on the tzurah, doesn’t require this).