One possible halachic problem that could arise is the possibility of indirect self-inflicted harm caused by someone else speaking lashon hara about you. This could lead to possible financial damage, and other forms of reputation damage, as well depending on how the girl and / or her parents, neighbors, etc. decide to retaliate.
Often, there is hidden enmity after a broken shidduch. Usually, that fades with time. However, if the shidduch-breaker recontacts, that enmity may be revived, and people involved may speak lashon hara. While this is their prohibition, there is a rule that you should not place yourself in a harmful situation, physically or emotionally, when there is a way to avoid it.
You cannot speak lashon hara about yourself directly or even give permission to others to speak lashon hara about you. Here, you are not giving permission to others to speak lashon hara about you, which seems worse, because by re-appearing in the picture, you may be causing it to occur, when you might have avoided it. See this M.Y. question as well as this one regarding speaking lashon hara about oneself.
I infer from Chafetz Chaim's rule that if you cannot give outright permission for someone to speak lashon hara about you, such as by telling him "Go speak lashon hara about me; I don't mind", then certainly you can't do this indirectly by creating a situation where it may be likely that they will speak lashon hara about you just by your presence or contact. That's in addition to the angle of avoiding situations that may cause yourself harm, when that's possible. (E.g.- Why would you go to a "hatefest" about you if you weren't invited?)