It’s possible that he gave her a pardon but didn’t announce it. She can then whip it out at anytime and try to walk from her crimes if it looks like she’s going to be convicted.
That would be like passing a law, but not publishing it.
If O. had signed an Executive Order pardoning H., it could not be concealed; it would have to be public knowledge. It's not like "Double Secret Probation."
Regards,
Bingo. Pardons manufactured like birth certificates when needed.