I'd say that a creature referring to “scientifically proving” the existence of something has adequately established the existence of consciousness.
Pondering the question of whether consciousness exists can only be done if consciousness does exist.
Most every human who can speak reports having beliefs and intentions, reports having engaged or planning to engage in willful actions; reports knowing something to be true; speaks of an “I”. How does one account for this universal experience (or these universal experiences) except as a product of consciousness? If people are deluded about--have false beliefs about--having beliefs, intentions, willful actions, awareness and knowledge of things and the self, then such delusions still just prove the existence of consciousness.
Lots of scientists during the past century have denied the thesis of determinism. My impression is that most physicists of the past century do not accept the thesis of determinism.
Moreover, I don't recall any scientist or philosopher claiming that the thesis of determinism implies that “consciousness is a fallacy”.
What does the phrase "consciousness is a fallacy" even mean? "Fallacy" means:
1. a deceptive, misleading, or false notion, belief, etc.:
That the world is flat was at one time a popular fallacy.
2. a misleading or unsound argument.
3. deceptive, misleading, or false nature; erroneousness.
4. Logic. any of various types of erroneous reasoning that render arguments logically unsound.
the definition of fallacy
All of these definitions of "fallacy" imply the existence of a faculty that can be deceived, have a false belief, engage in erroneous reasoning, etc.