I had to look that up.
Siddhis (Sanskrit and Pali : सिद्धि; Kannada: ಸಿದ್ಧಿ; Telugu: సిద్ధి; Tamil: சித்தி; Tibetan: དངོས་གྲུབ, THL: ngödrup,) are spiritual, paranormal, supernatural, or otherwise magical powers, abilities, and attainments that are the products of spiritual advancement through sādhanās such as meditation and yoga.
I don't believe there are any siddhis, no magical powers. To accept such things exist I think leaves us open to abuse by people who claim such powers. Rawat didn't misuse any powers - he pretended such powers existed and implied that he had them.
Maybe I'm getting too cynical though, as I don't believe in such a thing as spiritual advancement either. That baby went out with the bath water.