I have requested this question be moved over to the plumeria forum. I wouldn't want you to miss any good ideas.
I have been unsuccessful rooting 3 red plumeria. Some will tell you the reds are hard to root. But I gifted one to my GF who knows nothing about plumeria. Not only did it root, it thrives and flowers! Me, I still don't own a red.
It sounds like your cutting is alive. The wrinkling is normal. I would continue to monitor it, keeping it in bright shade. What kind of soil is it planted in?
