I had a particularly nasty ex - who broke up with me via something similar to IM, that we had on our campus computer system.
A few months later, I met my husband, and not too long after that, we got engaged.
A couple of months after I got engaged, I got an "IM" from my ex, saying "Please forgive me for breaking up with you by IM, and btw, I'm engaged."
Fortunately for his fiancee, she dumped his ass
I suspect he just proposed to her because his ex (I) was engaged, and he couldn't let me show him up...