I have been dealing with a guy friend with bipolar?

Can individuals with bipolar comprehend their feelings? For example do they know the difference between between BEING IN LOVE & LOVING, (CARING) for someone? And do people with bipolar lie allot? My friend with bipolar has extreme mood swings and he is medicated quite a bit. However, after sharing our lives together for several years he just VANISHED POOF he was gone like a GENIE IN A BOTTLE. I went to the extreme to educate myself with his bipolar just so that I would know what kind of signs to look for. I know that change does not work well with people who have bipolar. And he and I are so compatible I knew what he felt like I know what yearned for everything was so right. I feel like I have been lied to to there is no healing for me to move on. But yet, I feel like he is going through a different stage. Do bipolar people comprehend anything at all in how they make people feel. He is always changing his medications and to this day he is not the man I meet and like he never knew me. What is that about? I want to give him the benefit of the doubt but so confused please help me so I can at least try to move on.