Teshuva with HKBH's help

I was learning a piece of Siddura Shel Shabbos recently and he quoted a very interesting idea from the Chovos HaLevavos. When a person does an aveirah, there are times when a person can not do a complete teshuva because the residue of the aveirah is still around. Teh examples brought are someone who has a relationship that creates a mamzer. You can do teshuva for the aveirah but there will always be a blemish on your record kol z'man the mamzer is alive. The Chovos HaLevavos says an incredible chiddush. HKBH can step in and cause the mamzer to die so that you will now be able to receive a complete teshuva. To me this is a big chiddush-someone will die so you can benefit from a complete teshuva. The Siddura Shel Shabbos brings a less radical example of someone who steals money and doesn't know who to return the money to. HKBH will cause the nigzal to decide to forgive the robber and be mocheil the money.

With this understanding the Siddura Shel Shabbos explains the pesukim in Netzavim of "lo nifleisi hi mimcha...". (I don't recall the exact place where it is discussed. I will look it up and add it here).