I had a great friendship of over a decade, we were very close. Fell out oddly and stupidly years ago - frustrating because there wasn't even a row as such
We were just both in quite a bad place.
I tried contacting her a handful of times during the first year after the fall out, but she never replied. So I assume it was a bigger thing than I really knew about - that there was obviously a problem I was unaware of, and she didn't want to be friends, and that was that.
Once a year or so she crosses my mind and I hope she's doing well (which I'm sure she is) and it's just kinda wistful. I could never get in touch now, too long has passed and there's no way we could ever go back to the friendship. I'm grateful that we had the fun and laughs we did have, though 
These ghosts of friendship from the past are poignant.
Isn't it annoying and stupid sometimes how unfortunately things can work out, and you lose a friend you never thought you'd lose?
Has similar ever happened to you? Has anyone actually ever revived an old friendship?