Spirit guides and other important spiritual beings mostly communicate only with your subconsciousness. So, your conscious mind don´t need to have contact. You can notice some feelings without reason coming from somewhere in subconsciousness. Unconscious mind has more powerful communication potential, so it is better for your guide. Your guide wants to explain you something, but conscious mind can´t accept or understand many things. Only unconscious mind can understand everything. Seeing a physical person is only a form of being you can accept. Guide is in astral with no physical form. Guide´s body is only his interpretation in your mind. So, if you are in a good state of mind to astral, you can percieve this interpretation.