Siddha Yogi-s are known to be capable of appearing and disappearing at will. How do they accomplish that ? There are two ways through which a Siddha Yogi renders himself invisible and visible to others – 

• FIRST  We all are endowed with two faculties of cognition - Faculty to behold others and the faculty to be beheld by others. Siddha Yogi-s are empowered/capable of withdrawing their faculty of being beheld by others selectively while being able to behold others as before. Once they do so, nobody can behold them though they may be standing right next to you ! Certainly, they can behold anyone and everyone even in that state of imperceptibility without being beheld by anyone and everyone.  
   
• SECOND  Siddha Yogi-s are endowed with the faculty annihilating themselves by de-materialising their bodies into most fundamental elemental constituents of five Bhuta-s or even three Tanmatra-s of Sattva, Raja and Tama. Then they disappear for sure. Then you are amazed at their disappearance !! Further, they can re-appear by re-materialising themselves at their will with the same cosmic building blocks of five Bhuta-s and three Tanmatra-s governed by the DNA of past unredeemed Karma-s.  

Incidentally, the billion $ project to discover 'Higgs-Boson Particles', also known as 'God Particles', at Geneva is nothing but searching those three Tanmatra-s of Sattva, Raja and Tama, most fundamental cosmic building blocks of the universe. What they have not yet been able to establish after spending billions of $, was discovered / established / proved / authenticated by our ancestors, Rsi-s and Maharsi-s thousands of years ago....with their laboratories located under banyan trees surrounded by scientific equipment like Rudraksa Mala, Kamandala, Asana, Cimta, Gangajala ...!!!!!!!!!  

For such accomplished, highly advanced Souls, bodies are just building-block toys. They play with that joyously. Nobel Prizes shall be honoured if awarded to them individually, even if posthumously. Do you find it worth trying !!