[tinco]

Yes absolutely possible and also precisely the reason we are looking at these particles. The way science works is that we call these "assumptions" laws because we have never seen them broken and if we do it's likely some other assumption is wrong or our measurements are incorrect. But physics is always based on experiments, and if an experiment would show a violation of the law of conservation, and that experiment is repeatable and no one can find a flaw in it, then the law is changed.

And this is not some idle theory based in idealism, it actually happened in a super real way multiple times the most famous one being when we dropped the Newtonian "laws" for special relativity and quantum physics. No one liked it, no one was happy with it, but physics is about what happens in reality, and reality is what dictates what the laws are.

You probably get some downvotes for the UFO thing, but it doesn't really matter. Scientists don't need UFO's to question their assumptions, but they can be fine inspiration regardless.