Existence is the only reality for the self. As water cannot be separated from wetness, so you, the self, cannot be separated from existence. Existence is an integral aspect of your essence.
You don’t need to have an out-of-body experience in order to know that your existence does not depend on the existence of your body.
In the same way that the passing of the “childhood” body does not bring about the cessation of your (the self’s) existence, so the passing away of the “old” body will not bring about the cessation of your existence.