Truth be told I'm not social and I really don't have many close friends but I don't believe I am hikikomori.
Would my lack of a social network work against me in this regard because the gov't isn't able to make a case that I'm not about to go selling secrets to the PRC or Iran?

Honestly, they didn't ask me much about my friends. They did ask about my neighbors who have known me for a long time. They'll want to know every place where you've lived for the past 5-10 years, all of the jobs you've had (and probably the reason you left them), and related matters. They'll check your credit history to see if you have money problems and also check to see if you've ever been arrested.

Tell the truth to the best of your knowledge. If they catch you being less than honest, your chances of getting a clearance are almost nil. As a frame of reference, my wife was born in the Philippines so I have many relatives there. I also admitted to trying an illegal substance when in high school yet I still have a high clearance.

Anyway one of the sad things is that once my friend got a security clearance it seems that he's completely distanced himself from me as a friend after six years.

This may or may not have anything to do with his security clearance. People change and friendships do, too. For example, if he's married and you're still single, that could be a factor because married people are more likely to hang out with other married people. There are many people that I had as friends in school that I have not seen in decades. It just happens.