Sorry maybe I should have explained my comment

What you wrote does not really make sense in english and what the the other´s wrote is how I would have said it..

If you wanted to suggest another way similar to your idea it could be ..the "forgiven but never forgot/ forgotten thing"

Forgive but never forget is more of a statement, when you add ´thing´ to it it does not work

Oh! Sorry you misunderstood 

Thank you so much guys