I've found in life that when you think you've lost your best friend, it's usually a case of miscommunication.
My bestie that's been my buddy for more than half of my life and I got into it last year, because I felt that I was the only one who cared. I set up all of the times to hang out, etc. So I sent her this looooooooong message telling her how I felt, and we messaged back and forth a few times, and came out to still being friends lol. Don't know why we put up with each other, we're complete opposites. We were there for the hard times though, and that's what really counts.