You ask for logical fallacies. So I'm trying to answer on that basis.
You must be careful about mixing terms such as scientific fact and logical fact. They are not quite the same thing. So, logically, taking a scientific fact as a premise is somewhat different from taking a logical fact as a given. Matter-energy conservation is not quite on the same level as "If A implies B then not-B implies not-A."
The scientific fact is that certain kinds of things are conserved. Not any old thing, just certain ones.
So there are a number of conservation laws. Baryon number seems to be one. Examples of Baryons are protons and neutrons. So a colorful expression of the idea is "protons are forever." Insert a bunch of tedious stuff about nuclear interactions, Baryon resonances, etc. and tedious etc. But the general upshot is, there is a number that represents how many Baryons there are now. And this number does not change.
A Baryon is a thing. And yes, they don't disappear, only change into other Baryons, such that the total number is the same.
Some things are conserved.
Now, what about conditions? Consider that there are 5 objects at rest here, and 2 at rest over there. Say "here" is on my desk, and "there" is 50 km away. Later there are 4 here, and 2 over there, and one quickly moving from here to there. These two arrangements of things are not the same. It's a new arrangement, not just a change of the old arrangement into something else. The old arrangement no longer exists. The new arrangement has been created. The old arrangement was 5 objects at rest here and 2 at rest there. The new one is 4 at rest here, 2 at rest there, and 1 moving. The moving arrangement is entirely new. The "at rest" arrangement has stopped existing, replaced by the "something moving" arrangement.
Arrangements of things are not conserved. In the example, "at rest" is not conserved.
Also, you need to be careful about things that are not conserved. A photon, a particle of electromagnetic energy, can be created as desired. Indeed, your computer screen is probably creating a bunch of them right now as you read this. Photons have their own existence as discrete particles. Quantum weird particle-and-wave-at-the-same-time particles, maybe. But it's possible to detect them one at a time. And it's possible to generate arbitrarily large numbers of them where there were none before.
And the change in the objects that generate photons does not need to get rid of a thing. For example, an electron can move closer to the nucleus of an atom, and so give off a photon. Or a fast moving electron can bounce off other objects, and slow down, at the same time giving off a photon. These are changes in the arrangement of things, giving rise to new things.
Some things are not conserved.
So, the question is, what sort of category does consciousness fit in? Is it a conserved thing? A non-conserved condition? A non-conserved thing?
As far as conventional science, consciousness is a condition. Matter can become conscious, and later stop being conscious. Sure, the matter has simply changed form. The stuff that was conscious has not disappeared. But the arrangement of it that was conscious has started and then ceased existing.
