Nothing in science is ever proven .
Strictly speaking, you're right, but it's practically senseless since it would restrain scientific proof to the realm of logic and mathematics, both purely theoretical constructs. Besides, it exlcudes the possibility of distinguishing between the probable and the improbable, leading to unbridled empirical relativism (and nihilism?).
It's therefore more useful to use the definition 'compelling evidence' for scientific proof. In this case, evolution has been proven.