What you may want to do with plumeria - is put Christmas-type lights on it with a timer to keep it warm over the winter months. This has worked for an area above me (as in higher elevation) that gets hard freezes (which kill plumeria)- and they’ve had success with this.
Sorry yours didn’t survive. I love hibiscus but cannot grow the “fancy” verities that are grown in the South and in Hawaii - I’ve lost every one that I’ve tried. They shouldn’t even be sold here and I’ve learned my lesson.
If I ever try to work with plumeria up here again, I will try that trick! Great tip, thanks!