that’s the thing – we don’t know, and we assume it doesn’t, since if you ask them for an item, they give you that item, without mixing it with another item. as we said, if they did that, they would lose customers, as customers would be upset that they mixed up their foods with other foods they may not like.
this is why we can assume that there will not be any “visible trief or basar bcholov” in it, simply for obvious reasons. and if thats the case, then based on what we said above, we can consume a muffin (for example), since we use common sense, and assume that it is not mixed with anything else. obviously people can be machmir, which is seemingly the approach you are taking, which is completely understandable