acknowledging the existence of your body within a virtual reality VR experience
In physical reality and first order virtual reality there is something very simple that you can do to physically establish your presence. Look down, and you will see your body, or see parts of it continuously in peripheral vision.1
1. Slater, M. “Place Illusion and Plausibility Can Lead to Realistic Behaviour in Immersive Virtual Environments”Philos Trans R Soc Lond B Biol Sci. 2009 Dec 12; 364(1535): 3549–3557 Pg 10.