Something sort of like this may have happened to me once (I say may because it involves my lying bitch of a sister as an intermediary). We had some kind of thing going. Not sure what it was, probably just friends, but she had another guy she never told me about. After a while I made my peace with that, but it became clear that for whatever reason we couldn't be friends. I dashed off an angry (and frankly rather deranged, in retrospect) letter about how I loved her, how she hurt me, we could have been friends, yada yada. Probably not the best move on my part. Didn't call her again.
About three weeks later my sister told me she called. As I said above, my sister is a liar about nearly everything. I have no idea if this call actually took place. I didn't reply for something like a month and never heard from her again. In retrospect, if the call actually happened, she probably just wanted to apologize for letting me lead myself on and/or tell me I was absolutely batshit insane from what I wrote in the letter. Took me a hell of a long time to get over it, too.