Wenn Sie nicht denken, dann existieren Sie doch bestimmt, no doubt about it. Existieren (Dasein) is not the synonym of the transcendental apperception (Ich denke), so I don't see any legitimate philosophical ground for such an easy ontological implication.
Cogito ergo sum is not a mantra producing the existence of the cogitans, it is only an apodictic mark for the existence of a subject.